Upstream oodles of Chrome for Android code into Chromium.

chrome/android/java_staging/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutHelper.java

Index: chrome/android/java_staging/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutHelper.java
diff --git a/chrome/android/java_staging/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutHelper.java b/chrome/android/java_staging/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutHelper.java
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index 0000000000000000000000000000000000000000..10ea7e067674f9e638d0ceea92b3817b87aa1dab
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+++ b/chrome/android/java_staging/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutHelper.java
@@ -0,0 +1,1566 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.compositor.overlays.strip;
+
+import static org.chromium.chrome.browser.compositor.layouts.ChromeAnimation.AnimatableAnimation.createAnimation;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.os.Handler;
+import android.os.Message;
+import android.os.SystemClock;
+import android.view.View;
+import android.widget.AdapterView;
+import android.widget.AdapterView.OnItemClickListener;
+import android.widget.ArrayAdapter;
+import android.widget.ListPopupWindow;
+
+import com.google.android.apps.chrome.R;
+
+import org.chromium.base.PerfTraceEvent;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.SuppressFBWarnings;
+import org.chromium.chrome.browser.Tab;
+import org.chromium.chrome.browser.compositor.layouts.ChromeAnimation;
+import org.chromium.chrome.browser.compositor.layouts.ChromeAnimation.Animatable;
+import org.chromium.chrome.browser.compositor.layouts.ChromeAnimation.Animation;
+import org.chromium.chrome.browser.compositor.layouts.LayoutRenderHost;
+import org.chromium.chrome.browser.compositor.layouts.LayoutUpdateHost;
+import org.chromium.chrome.browser.compositor.layouts.components.CompositorButton;
+import org.chromium.chrome.browser.compositor.layouts.components.VirtualView;
+import org.chromium.chrome.browser.compositor.layouts.content.TabContentManager;
+import org.chromium.chrome.browser.compositor.layouts.phone.stack.StackScroller;
+import org.chromium.chrome.browser.compositor.overlays.strip.TabLoadTracker.TabLoadTrackerCallback;
+import org.chromium.chrome.browser.tabmodel.TabCreatorManager.TabCreator;
+import org.chromium.chrome.browser.tabmodel.TabModel;
+import org.chromium.chrome.browser.tabmodel.TabModelUtils;
+import org.chromium.chrome.browser.util.MathUtils;
+import org.chromium.ui.base.LocalizationUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This class handles managing the positions and behavior of all tabs in a tab strip.  It is
+ * responsible for both responding to UI input events and model change notifications, adjusting and
+ * animating the tab strip as required.
+ *
+ * <p>
+ * The stacking and visual behavior is driven by setting a {@link StripStacker}.
+ */
+public class StripLayoutHelper {
+    // Drag Constants
+    private static final int REORDER_SCROLL_NONE = 0;
+    private static final int REORDER_SCROLL_LEFT = 1;
+    private static final int REORDER_SCROLL_RIGHT = 2;
+
+    // Behavior Constants
+    private static final float EPSILON = 0.001f;
+    private static final int MAX_TABS_TO_STACK = 4;
+    private static final float TAN_OF_REORDER_ANGLE_START_THRESHOLD =
+            (float) Math.tan(Math.PI / 4.0f);
+    private static final float REORDER_OVERLAP_SWITCH_PERCENTAGE = 0.53f;
+
+    // Animation/Timer Constants
+    private static final int RESIZE_DELAY_MS = 1500;
+    private static final int SPINNER_UPDATE_DELAY_MS = 66;
+    // Degrees per milisecond.
+    private static final float SPINNER_DPMS = 0.33f;
+    private static final int EXPAND_DURATION_MS = 250;
+    private static final int ANIM_TAB_CREATED_MS = 150;
+    private static final int ANIM_TAB_CLOSED_MS = 150;
+    private static final int ANIM_TAB_RESIZE_MS = 150;
+    private static final int ANIM_TAB_MOVE_MS = 125;
+
+    // Visibility Constants
+    private static final float TAB_STACK_WIDTH_DP = 4.f;
+    private static final float TAB_OVERLAP_WIDTH_DP = 24.f;
+    private static final float MIN_TAB_WIDTH_DP = 190.f;
+    private static final float MAX_TAB_WIDTH_DP = 265.f;
+    private static final float REORDER_MOVE_START_THRESHOLD_DP = 50.f;
+    private static final float REORDER_EDGE_SCROLL_MAX_SPEED_DP = 1000.f;
+    private static final float REORDER_EDGE_SCROLL_START_MIN_DP = 87.4f;
+    private static final float REORDER_EDGE_SCROLL_START_MAX_DP = 18.4f;
+    private static final float NEW_TAB_BUTTON_Y_OFFSET_DP = 6.f;
+    private static final float NEW_TAB_BUTTON_CLICK_SLOP_DP = 4.f;
+    private static final float NEW_TAB_BUTTON_WIDTH_DP = 58.f;
+    private static final float NEW_TAB_BUTTON_HEIGHT_DP = 32.5f;
+
+    private static final int MESSAGE_RESIZE = 1;
+    private static final int MESSAGE_UPDATE_SPINNER = 2;
+
+    // External influences
+    private final LayoutUpdateHost mUpdateHost;
+    private final LayoutRenderHost mRenderHost;
+    private TabModel mModel;
+    private TabCreator mTabCreator;
+    private TabContentManager mTabContentManager;
+    private StripStacker mStripStacker = new StaticStripStacker();
+
+    // Internal State
+    private StripLayoutTab[] mStripTabs = new StripLayoutTab[0];
+    private StripLayoutTab[] mStripTabsVisuallyOrdered = new StripLayoutTab[0];
+    private StripLayoutTab[] mStripTabsToRender = new StripLayoutTab[0];
+    private final StripTabEventHandler mStripTabEventHandler = new StripTabEventHandler();
+    private final TabLoadTrackerCallback mTabLoadTrackerHost = new TabLoadTrackerCallbackImpl();
+    private ChromeAnimation<Animatable<?>> mLayoutAnimations;
+
+    private final CompositorButton mNewTabButton;
+
+    // Layout Constants
+    private final float mTabStackWidth;
+    private final float mTabOverlapWidth;
+    private float mNewTabButtonWidth;
+    private final float mMinTabWidth;
+    private final float mMaxTabWidth;
+    private final float mReorderMoveStartThreshold;
+    private final ListPopupWindow mTabMenu;
+
+    // Strip State
+    private StackScroller mScroller;
+    private int mScrollOffset;
+    private float mMinScrollOffset;
+    private float mCachedTabWidth;
+
+    // Reorder State
+    private int mReorderState = REORDER_SCROLL_NONE;
+    private boolean mInReorderMode = false;
+    private float mLastReorderX;
+    private long mLastReorderScrollTime;
+
+    // UI State
+    private StripLayoutTab mInteractingTab;
+    private CompositorButton mLastPressedCloseButton;
+    private float mWidth;
+    private float mHeight;
+    private long mLastSpinnerUpdate;
+    private float mLeftMargin;
+    private float mRightMargin;
+    private final boolean mIncognito;
+
+    // Tab menu item IDs
+    public static final int ID_CLOSE_ALL_TABS = 0;
+
+    private Context mContext;
+    /**
+     * Creates an instance of the {@link StripLayoutHelper}.
+     * @param context         The current Android {@link Context}.
+     * @param updateHost      The parent {@link LayoutUpdateHost}.
+     * @param renderHost      The {@link LayoutRenderHost}.
+     * @param incognito       Whether or not this tab strip is incognito.
+     */
+    public StripLayoutHelper(Context context, LayoutUpdateHost updateHost,
+            LayoutRenderHost renderHost, boolean incognito) {
+        mTabStackWidth = TAB_STACK_WIDTH_DP;
+        mTabOverlapWidth = TAB_OVERLAP_WIDTH_DP;
+        mNewTabButtonWidth = NEW_TAB_BUTTON_WIDTH_DP;
+
+        if (LocalizationUtils.isLayoutRtl()) {
+            // In rtl let the tab nest closer to the new tab button.
+            mNewTabButtonWidth -= mTabOverlapWidth / 2;
+        }
+        mRightMargin = LocalizationUtils.isLayoutRtl() ? 0 : mNewTabButtonWidth;
+        mLeftMargin = LocalizationUtils.isLayoutRtl() ? mNewTabButtonWidth : 0;
+        mMinTabWidth = MIN_TAB_WIDTH_DP;
+        mMaxTabWidth = MAX_TAB_WIDTH_DP;
+        mReorderMoveStartThreshold = REORDER_MOVE_START_THRESHOLD_DP;
+        mUpdateHost = updateHost;
+        mRenderHost = renderHost;
+        mNewTabButton =
+                new CompositorButton(context, NEW_TAB_BUTTON_WIDTH_DP, NEW_TAB_BUTTON_HEIGHT_DP);
+        mNewTabButton.setResources(R.drawable.btn_tabstrip_new_tab_normal,
+                R.drawable.btn_tabstrip_new_tab_pressed,
+                R.drawable.btn_tabstrip_new_incognito_tab_normal,
+                R.drawable.btn_tabstrip_new_incognito_tab_pressed);
+        mNewTabButton.setIncognito(incognito);
+        mNewTabButton.setY(NEW_TAB_BUTTON_Y_OFFSET_DP);
+        mNewTabButton.setClickSlop(NEW_TAB_BUTTON_CLICK_SLOP_DP);
+        Resources res = context.getResources();
+        mNewTabButton.setAccessibilityDescription(
+                res.getString(R.string.accessibility_toolbar_btn_new_tab),
+                res.getString(R.string.accessibility_toolbar_btn_new_incognito_tab));
+        mContext = context;
+        mIncognito = incognito;
+
+        // Create tab menu
+        mTabMenu = new ListPopupWindow(mContext);
+        mTabMenu.setAdapter(new ArrayAdapter<String>(mContext, R.layout.eb_popup_item,
+                new String[] {
+                        mContext.getString(!mIncognito ? R.string.menu_close_all_tabs
+                                                       : R.string.menu_close_all_incognito_tabs)}));
+        mTabMenu.setOnItemClickListener(new OnItemClickListener() {
+            @Override
+            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
+                mTabMenu.dismiss();
+                if (position == ID_CLOSE_ALL_TABS) {
+                    mModel.closeAllTabs(false, false);
+                }
+            }
+        });
+
+        int menuWidth = mContext.getResources().getDimensionPixelSize(R.dimen.menu_width);
+        mTabMenu.setWidth(menuWidth);
+        mTabMenu.setModal(true);
+    }
+
+    /**
+     * Get a list of virtual views for accessibility.
+     *
+     * @param views A List to populate with virtual views.
+     */
+    public void getVirtualViews(List<VirtualView> views) {
+        for (int i = mStripTabsToRender.length - 1; i >= 0; i--) {
+            StripLayoutTab tab = mStripTabsToRender[i];
+            tab.getVirtualViews(views);
+        }
+        if (mNewTabButton.isVisible()) views.add(mNewTabButton);
+    }
+
+    /**
+     * @return The visually ordered list of visible {@link StripLayoutTab}s.
+     */
+    @SuppressFBWarnings("EI_EXPOSE_REP")
+    public StripLayoutTab[] getStripLayoutTabsToRender() {
+        return mStripTabsToRender;
+    }
+
+    @VisibleForTesting
+    public int getTabCount() {
+        return mStripTabs.length;
+    }
+
+    /**
+     * @return A {@link CompositorButton} that represents the positioning of the new tab button.
+     */
+    public CompositorButton getNewTabButton() {
+        return mNewTabButton;
+    }
+
+    /**
+     * @return The brightness of background tabs in the tabstrip.
+     */
+    public float getStripBrightness() {
+        return mInReorderMode ? 0.75f : 1.0f;
+    }
+
+    /**
+     * Allows changing the visual behavior of the tabs in this stack, as specified by
+     * {@code stacker}.
+     * @param stacker The {@link StripStacker} that should specify how the tabs should be
+     *                presented.
+     */
+    public void setTabStacker(StripStacker stacker) {
+        if (stacker != mStripStacker) mUpdateHost.requestUpdate();
+        mStripStacker = stacker;
+
+        // Push Stacker properties to tabs.
+        for (int i = 0; i < mStripTabs.length; i++) {
+            pushStackerPropertiesToTab(mStripTabs[i]);
+        }
+    }
+
+    /**
+     * @parm margin The width of the distance between the left edge of
+     *              the screen and first tab.
+     */
+    public void setLeftMargin(float margin) {
+        mLeftMargin = margin;
+        mLeftMargin += LocalizationUtils.isLayoutRtl() ? mNewTabButtonWidth : 0;
+    }
+
+    /**
+     * @param margin The distance between the rightmost tab and the edge of the
+     *               screen.
+     */
+    public void setRightMargin(float margin) {
+        mRightMargin = margin;
+        mRightMargin += LocalizationUtils.isLayoutRtl() ? 0 : mNewTabButtonWidth;
+    }
+
+    /**
+     * Updates the size of the virtual tab strip, making the tabs resize and move accordingly.
+     * @param width  The new available width.
+     * @param height The new height this stack should be.
+     */
+    public void onSizeChanged(float width, float height) {
+        if (mWidth == width && mHeight == height) return;
+
+        boolean widthChanged = mWidth != width;
+
+        mWidth = width;
+        mHeight = height;
+
+        for (int i = 0; i < mStripTabs.length; i++) {
+            mStripTabs[i].setHeight(mHeight);
+        }
+
+        if (widthChanged) computeAndUpdateTabWidth(false);
+        if (mStripTabs.length > 0) mUpdateHost.requestUpdate();
+
+        // Dismiss tab menu, similar to how the app menu is dismissed on orientation change
+        mTabMenu.dismiss();
+    }
+
+    /**
+     * Updates all internal resources and dimensions.
+     * @param context The current Android {@link Context}.
+     */
+    public void onContextChanged(Context context) {
+        mScroller = new StackScroller(context);
+        mContext = context;
+    }
+
+    /**
+     * Notify the a title has changed.
+     *
+     * @param tabId     The id of the tab that has changed.
+     * @param title     The new title.
+     */
+    public void tabTitleChanged(int tabId, String title) {
+        StripLayoutTab tab = findTabById(tabId);
+        if (tab != null) tab.setAccessibilityDescription(title);
+    }
+
+    /**
+     * Sets the {@link TabModel} that this {@link StripLayoutHelper} will visually represent.
+     * @param model The {@link TabModel} to visually represent.
+     */
+    public void setTabModel(TabModel model, TabContentManager manager, TabCreator tabCreator) {
+        if (mModel == model) return;
+        mModel = model;
+        mTabContentManager = manager;
+        mTabCreator = tabCreator;
+        computeAndUpdateTabOrders(false);
+    }
+
+    /**
+     * Helper-specific updates. Cascades the values updated by the animations and flings.
+     * @param time The current time of the app in ms.
+     * @param dt   The delta time between update frames in ms.
+     * @return     Whether or not animations are done.
+     */
+    public boolean updateLayout(long time, long dt) {
+        PerfTraceEvent.instant("StripLayoutHelper:updateLayout");
+        final boolean doneAnimating = onUpdateAnimation(time, false);
+        updateStrip(time, dt);
+        return doneAnimating;
+    }
+
+    /**
+     * Called when a tab get selected.
+     * @param time   The current time of the app in ms.
+     * @param id     The id of the selected tab.
+     * @param prevId The id of the previously selected tab.
+     */
+    public void tabSelected(long time, int id, int prevId) {
+        if (findTabById(id) == null) {
+            tabCreated(time, id, prevId, true);
+        } else {
+            updateVisualTabOrdering();
+            mUpdateHost.requestUpdate();
+        }
+    }
+
+    /**
+     * Called when a tab has been moved in the tabModel.
+     * @param time     The current time of the app in ms.
+     * @param id       The id of the Tab.
+     * @param oldIndex The old index of the tab in the {@link TabModel}.
+     * @param newIndex The new index of the tab in the {@link TabModel}.
+     */
+    public void tabMoved(long time, int id, int oldIndex, int newIndex) {
+        reorderTab(id, oldIndex, newIndex, false);
+
+        updateVisualTabOrdering();
+        mUpdateHost.requestUpdate();
+    }
+
+    /**
+     * Called when a tab is being closed. When called, the closing tab will not
+     * be part of the model.
+     * @param time The current time of the app in ms.
+     * @param id   The id of the tab being closed.
+     */
+    public void tabClosed(long time, int id) {
+        if (findTabById(id) == null) return;
+
+        // 1. Find out if we're closing the last tab.  This determines if we resize immediately.
+        // We know mStripTabs.length >= 1 because findTabById did not return null.
+        boolean closingLastTab = mStripTabs[mStripTabs.length - 1].getId() == id;
+
+        // 2. Rebuild the strip.
+        computeAndUpdateTabOrders(!closingLastTab);
+
+        mUpdateHost.requestUpdate();
+    }
+
+    /**
+     * Called when a tab close has been undone and the tab has been restored.
+     * @param time The current time of the app in ms.
+     * @param id   The id of the Tab.
+     */
+    public void tabClosureCancelled(long time, int id) {
+        final boolean selected = TabModelUtils.getCurrentTabId(mModel) == id;
+        tabCreated(time, id, Tab.INVALID_TAB_ID, selected);
+    }
+
+    /**
+     * Called when a tab is created from the top left button.
+     * @param time     The current time of the app in ms.
+     * @param id       The id of the newly created tab.
+     * @param prevId   The id of the source tab.
+     * @param selected Whether the tab will be selected.
+     */
+    public void tabCreated(long time, int id, int prevId, boolean selected) {
+        if (findTabById(id) != null) return;
+
+        // 1. Build any tabs that are missing.
+        computeAndUpdateTabOrders(false);
+
+        // 2. Start an animation for the newly created tab.
+        StripLayoutTab tab = findTabById(id);
+        if (tab != null) startAnimation(buildTabCreatedAnimation(tab), true);
+
+        // 3. Figure out which tab needs to be visible.
+        StripLayoutTab fastExpandTab = findTabById(prevId);
+        boolean allowLeftExpand = false;
+        if (!selected) {
+            fastExpandTab = tab;
+            allowLeftExpand = true;
+        }
+
+        // 4. Scroll the stack so that the fast expand tab is visible.
+        if (fastExpandTab != null) {
+            float delta =
+                    calculateOffsetToMakeTabVisible(fastExpandTab, false, allowLeftExpand, true);
+            if (delta != 0.f) {
+                mScroller.startScroll(mScrollOffset, 0, (int) delta, 0, time, EXPAND_DURATION_MS);
+            }
+        }
+
+        mUpdateHost.requestUpdate();
+    }
+
+    /**
+     * Called when a tab has started loading.
+     * @param id The id of the Tab.
+     */
+    public void tabPageLoadStarted(int id) {
+        StripLayoutTab tab = findTabById(id);
+        if (tab != null) tab.pageLoadingStarted();
+    }
+
+    /**
+     * Called when a tab has finished loading.
+     * @param id The id of the Tab.
+     */
+    public void tabPageLoadFinished(int id) {
+        StripLayoutTab tab = findTabById(id);
+        if (tab != null) tab.pageLoadingFinished();
+    }
+
+    /**
+     * Called when a tab has started loading resources.
+     * @param id The id of the Tab.
+     */
+    public void tabLoadStarted(int id) {
+        StripLayoutTab tab = findTabById(id);
+        if (tab != null) tab.loadingStarted();
+    }
+
+    /**
+     * Called when a tab has stopped loading resources.
+     * @param id The id of the Tab.
+     */
+    public void tabLoadFinished(int id) {
+        StripLayoutTab tab = findTabById(id);
+        if (tab != null) tab.loadingFinished();
+    }
+
+    /**
+     * Called on touch drag event.
+     * @param time   The current time of the app in ms.
+     * @param x      The y coordinate of the end of the drag event.
+     * @param y      The y coordinate of the end of the drag event.
+     * @param deltaX The number of pixels dragged in the x direction.
+     * @param deltaY The number of pixels dragged in the y direction.
+     * @param totalX The total delta x since the drag started.
+     * @param totalY The total delta y since the drag started.
+     */
+    public void drag(
+            long time, float x, float y, float deltaX, float deltaY, float totalX, float totalY) {
+        resetResizeTimeout(false);
+
+        deltaX = MathUtils.flipSignIf(deltaX, LocalizationUtils.isLayoutRtl());
+
+        // 1. Reset the button state.
+        mNewTabButton.drag(x, y);
+        if (mLastPressedCloseButton != null) {
+            if (!mLastPressedCloseButton.drag(x, y)) mLastPressedCloseButton = null;
+        }
+
+        if (mInReorderMode) {
+            // 2.a. Handle reordering tabs.
+            // This isn't the accumulated delta since the beginning of the drag.  It accumulates
+            // the delta X until a threshold is crossed and then the event gets processed.
+            float accumulatedDeltaX = x - mLastReorderX;
+
+            if (Math.abs(accumulatedDeltaX) >= 1.f) {
+                if (!LocalizationUtils.isLayoutRtl()) {
+                    if (deltaX >= 1.f) {
+                        mReorderState |= REORDER_SCROLL_RIGHT;
+                    } else if (deltaX <= -1.f) {
+                        mReorderState |= REORDER_SCROLL_LEFT;
+                    }
+                } else {
+                    if (deltaX >= 1.f) {
+                        mReorderState |= REORDER_SCROLL_LEFT;
+                    } else if (deltaX <= -1.f) {
+                        mReorderState |= REORDER_SCROLL_RIGHT;
+                    }
+                }
+
+                mLastReorderX = x;
+                updateReorderPosition(accumulatedDeltaX);
+            }
+        } else if (!mScroller.isFinished()) {
+            // 2.b. Still scrolling, update the scroll destination here.
+            mScroller.setFinalX((int) (mScroller.getFinalX() + deltaX));
+        } else {
+            // 2.c. Not scrolling.  Check if we need to fast expand.
+            float fastExpandDelta =
+                    calculateOffsetToMakeTabVisible(mInteractingTab, true, true, true);
+
+            if (mInteractingTab != null && fastExpandDelta != 0.f) {
+                if ((fastExpandDelta > 0 && deltaX > 0) || (fastExpandDelta < 0 && deltaX < 0)) {
+                    mScroller.startScroll(
+                            mScrollOffset, 0, (int) fastExpandDelta, 0, time, EXPAND_DURATION_MS);
+                }
+            } else {
+                updateScrollOffsetPosition((int) (mScrollOffset + deltaX));
+            }
+        }
+
+        // 3. Check if we should start the reorder mode
+        if (!mInReorderMode) {
+            final float absTotalX = Math.abs(totalX);
+            final float absTotalY = Math.abs(totalY);
+            if (totalY > mReorderMoveStartThreshold && absTotalX < mReorderMoveStartThreshold * 2.f
+                    && (absTotalX > EPSILON
+                               && (absTotalY / absTotalX) > TAN_OF_REORDER_ANGLE_START_THRESHOLD)) {
+                startReorderMode(time, x, x - totalX);
+            }
+        }
+
+        // If we're scrolling at all we aren't interacting with any particular tab.
+        // We already kicked off a fast expansion earlier if we needed one.  Reorder mode will
+        // repopulate this if necessary.
+        if (!mInReorderMode) mInteractingTab = null;
+        mUpdateHost.requestUpdate();
+    }
+
+    /**
+     * Called on touch fling event. This is called before the onUpOrCancel event.
+     * @param time      The current time of the app in ms.
+     * @param x         The y coordinate of the start of the fling event.
+     * @param y         The y coordinate of the start of the fling event.
+     * @param velocityX The amount of velocity in the x direction.
+     * @param velocityY The amount of velocity in the y direction.
+     */
+    public void fling(long time, float x, float y, float velocityX, float velocityY) {
+        resetResizeTimeout(false);
+
+        velocityX = MathUtils.flipSignIf(velocityX, LocalizationUtils.isLayoutRtl());
+
+        // 1. If we're currently in reorder mode, don't allow the user to fling.
+        if (mInReorderMode) return;
+
+        // 2. If we're fast expanding or scrolling, figure out the destination of the scroll so we
+        // can apply it to the end of this fling.
+        int scrollDeltaRemaining = 0;
+        if (!mScroller.isFinished()) {
+            scrollDeltaRemaining = mScroller.getFinalX() - mScrollOffset;
+
+            mInteractingTab = null;
+            mScroller.forceFinished(true);
+        }
+
+        // 3. Kick off the fling.
+        mScroller.fling(
+                mScrollOffset, 0, (int) velocityX, 0, (int) mMinScrollOffset, 0, 0, 0, 0, 0, time);
+        mScroller.setFinalX(mScroller.getFinalX() + scrollDeltaRemaining);
+        mUpdateHost.requestUpdate();
+    }
+
+    /**
+     * Called on onDown event.
+     * @param time The time stamp in millisecond of the event.
+     * @param x    The x position of the event.
+     * @param y    The y position of the event.
+     */
+    public void onDown(long time, float x, float y) {
+        resetResizeTimeout(false);
+
+        if (mNewTabButton.onDown(x, y)) {
+            mRenderHost.requestRender();
+            return;
+        }
+
+        final StripLayoutTab clickedTab = getTabAtPosition(x);
+        final int index = clickedTab != null
+                ? TabModelUtils.getTabIndexById(mModel, clickedTab.getId())
+                : TabModel.INVALID_TAB_INDEX;
+        // http://crbug.com/472186 : Needs to handle a case that index is invalid.
+        // The case could happen when the current tab is touched while we're inflating the rest of
+        // the tabs from disk.
+        mInteractingTab = index != TabModel.INVALID_TAB_INDEX && index < mStripTabs.length
+                ? mStripTabs[index]
+                : null;
+        if (clickedTab != null && clickedTab.checkCloseHitTest(x, y)) {
+            clickedTab.setClosePressed(true);
+            mLastPressedCloseButton = clickedTab.getCloseButton();
+            mRenderHost.requestRender();
+        }
+
+        if (!mScroller.isFinished()) {
+            mScroller.forceFinished(true);
+            mInteractingTab = null;
+        }
+    }
+
+    /**
+     * Called on long press touch event.
+     * @param time The current time of the app in ms.
+     * @param x    The x coordinate of the position of the press event.
+     * @param y    The y coordinate of the position of the press event.
+     */
+    public void onLongPress(long time, float x, float y) {
+        final StripLayoutTab clickedTab = getTabAtPosition(x);
+        if (clickedTab != null && clickedTab.checkCloseHitTest(x, y)) {
+            clickedTab.setClosePressed(false);
+            mRenderHost.requestRender();
+            showTabMenu(clickedTab);
+        } else {
+            resetResizeTimeout(false);
+            startReorderMode(time, x, x);
+        }
+    }
+
+    /**
+     * Called on click. This is called before the onUpOrCancel event.
+     * @param time The current time of the app in ms.
+     * @param x    The x coordinate of the position of the click.
+     * @param y    The y coordinate of the position of the click.
+     */
+    public void click(long time, float x, float y) {
+        resetResizeTimeout(false);
+
+        if (mNewTabButton.click(x, y) && mModel != null) {
+            mTabCreator.launchNTP();
+            return;
+        }
+
+        final StripLayoutTab clickedTab = getTabAtPosition(x);
+        if (clickedTab == null || clickedTab.isDying()) return;
+        if (clickedTab.checkCloseHitTest(x, y)) {
+            // 1. Start the close animation.
+            startAnimation(buildTabClosedAnimation(clickedTab), true);
+
+            // 2. Set the dying state of the tab.
+            clickedTab.setIsDying(true);
+
+            // 3. Fake a selection on the next tab now.
+            Tab nextTab = mModel.getNextTabIfClosed(clickedTab.getId());
+            if (nextTab != null) tabSelected(time, nextTab.getId(), clickedTab.getId());
+
+            // 4. Find out if we're closing the last tab.  This determines if we resize immediately.
+            boolean lastTab = mStripTabs.length == 0
+                    || mStripTabs[mStripTabs.length - 1].getId() == clickedTab.getId();
+
+            // 5. Resize the tabs appropriately.
+            resizeTabStrip(!lastTab);
+        } else {
+            int newIndex = TabModelUtils.getTabIndexById(mModel, clickedTab.getId());
+            TabModelUtils.setIndex(mModel, newIndex);
+        }
+    }
+
+    /**
+     * Called on up or cancel touch events. This is called after the click and fling event if any.
+     * @param time The current time of the app in ms.
+     */
+    public void onUpOrCancel(long time) {
+        // 1. Reset the last close button pressed state.
+        if (mLastPressedCloseButton != null) mLastPressedCloseButton.onUpOrCancel();
+        mLastPressedCloseButton = null;
+
+        // 2. Stop any reordering that is happening.
+        stopReorderMode();
+
+        // 3. Reset state
+        mInteractingTab = null;
+        mReorderState = REORDER_SCROLL_NONE;
+        if (mNewTabButton.onUpOrCancel() && mModel != null) {
+            mTabCreator.launchNTP();
+        }
+    }
+
+    private boolean onUpdateAnimation(long time, boolean jumpToEnd) {
+        // 1. Handle any Scroller movements (flings).
+        if (!jumpToEnd) updateScrollOffset(time);
+
+        // 2. Handle reordering automatically scrolling the tab strip.
+        handleReorderAutoScrolling(time);
+
+        // 3. Handle layout-wide animations.
+        boolean update = false;
+        boolean finished = true;
+        if (mLayoutAnimations != null) {
+            if (jumpToEnd) {
+                finished = mLayoutAnimations.finished();
+            } else {
+                finished = mLayoutAnimations.update(time);
+            }
+            if (jumpToEnd || finished) finishAnimation();
+
+            update = true;
+        }
+
+        // 4. Handle tab-specific content animations.
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+            if (tab.isAnimating()) {
+                update = true;
+                finished &= tab.onUpdateAnimation(time, jumpToEnd);
+            }
+        }
+
+        // 5. Update tab spinners.
+        updateSpinners(time);
+
+        // 6. Stop any flings if we're trying to stop animations.
+        if (jumpToEnd) mScroller.forceFinished(true);
+
+        // 7. Request another update if anything requires it.
+        if (update) mUpdateHost.requestUpdate();
+
+        return finished;
+    }
+
+    /**
+     * @return Whether or not the tabs are moving.
+     */
+    @VisibleForTesting
+    public boolean isAnimating() {
+        return mLayoutAnimations != null || !mScroller.isFinished();
+    }
+
+    /**
+     * Finishes any outstanding animations and propagates any related changes to the
+     * {@link TabModel}.
+     */
+    public void finishAnimation() {
+        if (mLayoutAnimations == null) return;
+
+        // 1. Force any outstanding animations to finish.
+        mLayoutAnimations.updateAndFinish();
+        mLayoutAnimations = null;
+
+        // 2. Figure out which tabs need to be closed.
+        ArrayList<StripLayoutTab> tabsToRemove = new ArrayList<StripLayoutTab>();
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+            if (tab.isDying()) tabsToRemove.add(tab);
+        }
+
+        // 3. Pass the close notifications to the model.
+        for (StripLayoutTab tab : tabsToRemove) {
+            TabModelUtils.closeTabById(mModel, tab.getId(), true);
+        }
+
+        if (!tabsToRemove.isEmpty()) mUpdateHost.requestUpdate();
+    }
+
+    private void startAnimation(Animation<Animatable<?>> animation, boolean finishPrevious) {
+        if (finishPrevious) finishAnimation();
+
+        if (mLayoutAnimations == null) {
+            mLayoutAnimations = new ChromeAnimation<ChromeAnimation.Animatable<?>>();
+        }
+
+        mLayoutAnimations.add(animation);
+
+        mUpdateHost.requestUpdate();
+    }
+
+    private void cancelAnimation(StripLayoutTab tab, StripLayoutTab.Property property) {
+        if (mLayoutAnimations == null) return;
+        mLayoutAnimations.cancel(tab, property);
+    }
+
+    private void updateSpinners(long time) {
+        long diff = time - mLastSpinnerUpdate;
+        float degrees = diff * SPINNER_DPMS;
+        boolean tabsToLoad = false;
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+            // TODO(clholgat): Only update if the tab is visible.
+            if (tab.isLoading()) {
+                tab.addLoadingSpinnerRotation(degrees);
+                tabsToLoad = true;
+            }
+        }
+        mLastSpinnerUpdate = time;
+        if (tabsToLoad) {
+            mStripTabEventHandler.removeMessages(MESSAGE_UPDATE_SPINNER);
+            mStripTabEventHandler.sendEmptyMessageDelayed(
+                    MESSAGE_UPDATE_SPINNER, SPINNER_UPDATE_DELAY_MS);
+        }
+    }
+
+    private void updateScrollOffsetPosition(int pos) {
+        int oldScrollOffset = mScrollOffset;
+        mScrollOffset = MathUtils.clamp(pos, (int) mMinScrollOffset, 0);
+
+        if (mInReorderMode && mScroller.isFinished()) {
+            int delta = MathUtils.flipSignIf(
+                    oldScrollOffset - mScrollOffset, LocalizationUtils.isLayoutRtl());
+            updateReorderPosition(delta);
+        }
+    }
+
+    private void updateScrollOffset(long time) {
+        if (mScroller.computeScrollOffset(time)) {
+            updateScrollOffsetPosition(mScroller.getCurrX());
+            mUpdateHost.requestUpdate();
+        }
+    }
+
+    private void updateScrollOffsetLimits() {
+        // 1. Compute the width of the available space for all tabs.
+        float stripWidth = mWidth - mLeftMargin - mRightMargin;
+
+        // 2. Compute the effective width of every tab.
+        float tabsWidth = 0.f;
+        for (int i = 0; i < mStripTabs.length; i++) {
+            final StripLayoutTab tab = mStripTabs[i];
+            tabsWidth += (tab.getWidth() - mTabOverlapWidth) * tab.getWidthWeight();
+        }
+
+        // 3. Correct fencepost error in tabswidth;
+        tabsWidth = tabsWidth + mTabOverlapWidth;
+
+        // 4. Calculate the minimum scroll offset.  Round > -EPSILON to 0.
+        mMinScrollOffset = Math.min(0.f, stripWidth - tabsWidth);
+        if (mMinScrollOffset > -EPSILON) mMinScrollOffset = 0.f;
+
+        // 5. Clamp mScrollOffset to make sure it's in the valid range.
+        updateScrollOffsetPosition(mScrollOffset);
+    }
+
+    private void computeAndUpdateTabOrders(boolean delayResize) {
+        final int count = mModel.getCount();
+        StripLayoutTab[] tabs = new StripLayoutTab[count];
+
+        for (int i = 0; i < count; i++) {
+            int id = mModel.getTabAt(i).getId();
+            StripLayoutTab oldTab = findTabById(id);
+            tabs[i] = oldTab != null ? oldTab : createStripTab(id);
+            tabs[i].setAccessibilityDescription(mModel.getTabAt(i).getTitle());
+        }
+
+        int oldStripLength = mStripTabs.length;
+        mStripTabs = tabs;
+
+        if (mStripTabs.length != oldStripLength) resizeTabStrip(delayResize);
+
+        updateVisualTabOrdering();
+    }
+
+    private void resizeTabStrip(boolean delay) {
+        if (delay) {
+            resetResizeTimeout(true);
+        } else {
+            computeAndUpdateTabWidth(true);
+        }
+    }
+
+    private void updateVisualTabOrdering() {
+        if (mStripTabs.length != mStripTabsVisuallyOrdered.length) {
+            mStripTabsVisuallyOrdered = new StripLayoutTab[mStripTabs.length];
+        }
+
+        mStripStacker.createVisualOrdering(mModel.index(), mStripTabs, mStripTabsVisuallyOrdered);
+    }
+
+    private StripLayoutTab createStripTab(int id) {
+        // TODO: Cache these
+        StripLayoutTab tab =
+                new StripLayoutTab(mContext, id, mTabLoadTrackerHost, mRenderHost, mIncognito);
+        tab.setHeight(mHeight);
+        pushStackerPropertiesToTab(tab);
+        return tab;
+    }
+
+    private void pushStackerPropertiesToTab(StripLayoutTab tab) {
+        tab.setCanShowCloseButton(mStripStacker.canShowCloseButton());
+        // TODO(dtrainor): Push more properties as they are added (title text slide, etc?)
+    }
+
+    /**
+     * @param id The Tab id.
+     * @return The StripLayoutTab that corresponds to that tabid.
+     */
+    @VisibleForTesting
+    public StripLayoutTab findTabById(int id) {
+        if (mStripTabs == null) return null;
+        for (int i = 0; i < mStripTabs.length; i++) {
+            if (mStripTabs[i].getId() == id) return mStripTabs[i];
+        }
+        return null;
+    }
+
+    private int findIndexForTab(int id) {
+        if (mStripTabs == null) return TabModel.INVALID_TAB_INDEX;
+        for (int i = 0; i < mStripTabs.length; i++) {
+            if (mStripTabs[i].getId() == id) return i;
+        }
+        return TabModel.INVALID_TAB_INDEX;
+    }
+
+    private void computeAndUpdateTabWidth(boolean animate) {
+        // Remove any queued resize messages.
+        mStripTabEventHandler.removeMessages(MESSAGE_RESIZE);
+
+        int numTabs = Math.max(mStripTabs.length, 1);
+
+        // 1. Compute the width of the available space for all tabs.
+        float stripWidth = mWidth - mLeftMargin - mRightMargin;
+
+        // 2. Compute additional width we gain from overlapping the tabs.
+        float overlapWidth = mTabOverlapWidth * (numTabs - 1);
+
+        // 3. Calculate the optimal tab width.
+        float optimalTabWidth = (stripWidth + overlapWidth) / numTabs;
+
+        // 4. Calculate the realistic tab width.
+        mCachedTabWidth = MathUtils.clamp(optimalTabWidth, mMinTabWidth, mMaxTabWidth);
+
+        // 5. Propagate the tab width to all tabs.
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+            if (tab.isDying()) continue;
+
+            // 5.a. Cancel any outstanding tab width animations.
+            cancelAnimation(mStripTabs[i], StripLayoutTab.Property.WIDTH);
+
+            if (animate) {
+                startAnimation(buildTabResizeAnimation(tab, mCachedTabWidth), false);
+            } else {
+                mStripTabs[i].setWidth(mCachedTabWidth);
+            }
+        }
+    }
+
+    private void updateStrip(long time, long dt) {
+        if (mModel == null) return;
+
+        // TODO(dtrainor): Remove this once tabCreated() is refactored to be called even from
+        // restore.
+        if (mStripTabs == null || mModel.getCount() != mStripTabs.length) {
+            computeAndUpdateTabOrders(false);
+        }
+
+        // 1. Update the scroll offset limits
+        updateScrollOffsetLimits();
+
+        // 2. Calculate the ideal tab positions
+        computeTabInitialPositions();
+
+        // 3. Calculate the tab stacking.
+        computeTabOffsetHelper();
+
+        // 4. Calculate which tabs are visible.
+        mStripStacker.performOcclusionPass(mModel.index(), mStripTabs);
+
+        // 5. Create render list.
+        createRenderList();
+
+        // 6. Figure out where to put the new tab button.
+        updateNewTabButtonState();
+
+        // 7. Check if we have any animations and request an update if so.
+        for (int i = 0; i < mStripTabs.length; i++) {
+            if (mStripTabs[i].isAnimating()) {
+                mUpdateHost.requestUpdate();
+                break;
+            }
+        }
+    }
+
+    private void computeTabInitialPositions() {
+        // Shift all of the tabs over by the the left margin because we're
+        // no longer base lined at 0
+        float tabPosition;
+        if (!LocalizationUtils.isLayoutRtl()) {
+            tabPosition = mScrollOffset + mLeftMargin;
+        } else {
+            tabPosition = mWidth - mCachedTabWidth - mScrollOffset - mRightMargin;
+        }
+
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+            tab.setIdealX(tabPosition);
+            float delta = (tab.getWidth() - mTabOverlapWidth) * tab.getWidthWeight();
+            delta = MathUtils.flipSignIf(delta, LocalizationUtils.isLayoutRtl());
+            tabPosition += delta;
+        }
+    }
+
+    private void computeTabOffsetHelper() {
+        final int selIndex = mModel.index();
+
+        // 1. Calculate the size of the selected tab.  This is used later to figure out how
+        // occluded the tabs are.
+        final StripLayoutTab selTab = selIndex >= 0 ? mStripTabs[selIndex] : null;
+        final float selTabWidth = selTab != null ? selTab.getWidth() : 0;
+        final float selTabVisibleSize = selTabWidth - mTabStackWidth - mTabOverlapWidth;
+
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+
+            float posX = tab.getIdealX();
+
+            // 2. Calculate how many tabs are stacked on the left or the right, giving us an idea
+            // of where we can stack this current tab.
+            int leftStackCount = (i < selIndex) ? Math.min(i, MAX_TABS_TO_STACK)
+                                                : Math.min(MAX_TABS_TO_STACK, selIndex)
+                            + Math.min(MAX_TABS_TO_STACK, i - selIndex);
+
+            int rightStackCount = (i >= selIndex)
+                    ? Math.min(mStripTabs.length - 1 - i, MAX_TABS_TO_STACK)
+                    : Math.min(mStripTabs.length - 1 - selIndex, MAX_TABS_TO_STACK)
+                            + Math.min(selIndex - i, MAX_TABS_TO_STACK);
+
+            if (LocalizationUtils.isLayoutRtl()) {
+                int oldLeft = leftStackCount;
+                leftStackCount = rightStackCount;
+                rightStackCount = oldLeft;
+            }
+
+            // 3. Calculate the proper draw position for the tab.  Clamp based on stacking
+            // rules.
+            float minDrawX = mTabStackWidth * leftStackCount + mLeftMargin;
+            float maxDrawX = mWidth - mTabStackWidth * rightStackCount - mRightMargin;
+
+            float drawX =
+                    MathUtils.clamp(posX + tab.getOffsetX(), minDrawX, maxDrawX - tab.getWidth());
+
+            // TODO(dtrainor): Don't set drawX if the tab is closing?
+            tab.setDrawX(drawX);
+            tab.setDrawY(tab.getOffsetY());
+
+            // 4. Calculate how visible this tab is.
+            float visiblePercentage = 1.f;
+            if (i != selIndex) {
+                final float effectiveTabWidth = Math.max(tab.getWidth(), 1.f);
+                final boolean leftStack =
+                        LocalizationUtils.isLayoutRtl() ? i > selIndex : i < selIndex;
+                final float minVisible = !leftStack ? minDrawX + selTabVisibleSize : minDrawX;
+                final float maxVisible = leftStack ? maxDrawX - selTabVisibleSize : maxDrawX;
+
+                final float clippedTabWidth =
+                        Math.min(posX + effectiveTabWidth, maxVisible) - Math.max(posX, minVisible);
+                visiblePercentage = MathUtils.clamp(clippedTabWidth / effectiveTabWidth, 0.f, 1.f);
+            }
+            tab.setVisiblePercentage(visiblePercentage);
+
+            // 5. Calculate which index we start sliding content for.
+            // When reordering, we don't want to slide the content of the adjacent tabs.
+            int contentOffsetIndex = mInReorderMode ? selIndex + 1 : selIndex;
+
+            // 6. Calculate how much the tab is overlapped on the left side or right for RTL.
+            float hiddenAmount = 0.f;
+            if (i > contentOffsetIndex && i > 0 && mStripStacker.canSlideTitleText()) {
+                // 6.a. Get the effective right edge of the previous tab.
+                final StripLayoutTab prevTab = mStripTabs[i - 1];
+                final float prevLayoutWidth =
+                        (prevTab.getWidth() - mTabOverlapWidth) * prevTab.getWidthWeight();
+                float prevTabRight = prevTab.getDrawX();
+                if (!LocalizationUtils.isLayoutRtl()) prevTabRight += prevLayoutWidth;
+
+                // 6.b. Subtract our current draw X from the previous tab's right edge and
+                // get the percentage covered.
+                hiddenAmount = Math.max(prevTabRight - drawX, 0);
+                if (LocalizationUtils.isLayoutRtl()) {
+                    // Invert The amount because we're RTL.
+                    hiddenAmount = prevLayoutWidth - hiddenAmount;
+                }
+            }
+
+            tab.setContentOffsetX(hiddenAmount);
+        }
+    }
+
+    private void createRenderList() {
+        // 1. Figure out how many tabs will need to be rendered.
+        int renderCount = 0;
+        for (int i = 0; i < mStripTabsVisuallyOrdered.length; ++i) {
+            if (mStripTabsVisuallyOrdered[i].isVisible()) renderCount++;
+        }
+
+        // 2. Reallocate the render list if necessary.
+        if (mStripTabsToRender.length != renderCount) {
+            mStripTabsToRender = new StripLayoutTab[renderCount];
+        }
+
+        // 3. Populate it with the visible tabs.
+        int renderIndex = 0;
+        for (int i = 0; i < mStripTabsVisuallyOrdered.length; ++i) {
+            if (mStripTabsVisuallyOrdered[i].isVisible()) {
+                mStripTabsToRender[renderIndex++] = mStripTabsVisuallyOrdered[i];
+            }
+        }
+    }
+
+    private void updateNewTabButtonState() {
+        // 1. Don't display the new tab button if we're in reorder mode.
+        if (mInReorderMode || mStripTabs.length == 0) {
+            mNewTabButton.setVisible(false);
+            return;
+        }
+        mNewTabButton.setVisible(true);
+
+        float leftEdge = mWidth - mRightMargin;
+        float rightEdge = mLeftMargin;
+
+        for (int i = 0; i < mStripTabs.length; i++) {
+            StripLayoutTab tab = mStripTabs[i];
+            float layoutWidth = (tab.getWidth() - mTabOverlapWidth) * tab.getWidthWeight();
+            rightEdge = Math.max(tab.getDrawX() + layoutWidth, rightEdge);
+            leftEdge = Math.min(tab.getDrawX(), leftEdge);
+        }
+        rightEdge = Math.min(rightEdge + mTabOverlapWidth, mWidth - mRightMargin);
+        leftEdge = Math.max(leftEdge, mLeftMargin);
+
+        rightEdge -= mTabOverlapWidth / 2;
+
+        // 3. Position the new tab button.
+        if (!LocalizationUtils.isLayoutRtl()) {
+            mNewTabButton.setX(rightEdge);
+        } else {
+            mNewTabButton.setX(leftEdge - mNewTabButtonWidth);
+        }
+    }
+
+    private float calculateOffsetToMakeTabVisible(StripLayoutTab tab, boolean canExpandSelectedTab,
+            boolean canExpandLeft, boolean canExpandRight) {
+        if (tab == null) return 0.f;
+
+        final int selIndex = mModel.index();
+        final int index = TabModelUtils.getTabIndexById(mModel, tab.getId());
+
+        // 1. The selected tab is always visible.  Early out unless we want to unstack it.
+        if (selIndex == index && !canExpandSelectedTab) return 0.f;
+
+        // TODO(dtrainor): Use real tab widths here?
+        float stripWidth = mWidth - mLeftMargin - mRightMargin;
+        final float tabWidth = mCachedTabWidth - mTabOverlapWidth;
+
+        // TODO(dtrainor): Handle maximum number of tabs that can be visibly stacked in these
+        // optimal positions.
+
+        // 2. Calculate the optimal minimum and maximum scroll offsets to show the tab.
+        float optimalLeft = -index * tabWidth;
+        float optimalRight = stripWidth - (index + 1) * tabWidth;
+
+        // 3. Account for the selected tab always being visible.  Need to buffer by one extra
+        // tab width depending on if the tab is to the left or right of the selected tab.
+        if (index < selIndex) {
+            optimalRight -= tabWidth;
+        } else if (index > selIndex) {
+            optimalLeft += tabWidth;
+        }
+
+        // 4. Return the proper deltaX that has to be applied to the current scroll to see the
+        // tab.
+        if (mScrollOffset < optimalLeft && canExpandLeft) {
+            return optimalLeft - mScrollOffset;
+        } else if (mScrollOffset > optimalRight && canExpandRight) {
+            return optimalRight - mScrollOffset;
+        }
+
+        // 5. We don't have to do anything.  Return no delta.
+        return 0.f;
+    }
+
+    private StripLayoutTab getTabAtPosition(float x) {
+        for (int i = mStripTabsVisuallyOrdered.length - 1; i >= 0; i--) {
+            final StripLayoutTab tab = mStripTabsVisuallyOrdered[i];
+            if (tab.isVisible() && tab.getDrawX() <= x && x <= (tab.getDrawX() + tab.getWidth())) {
+                return tab;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * @param tab The StripLayoutTab to look for.
+     * @return The index of the tab in the visual ordering.
+     */
+    @VisibleForTesting
+    public int visualIndexOfTab(StripLayoutTab tab) {
+        for (int i = 0; i < mStripTabsVisuallyOrdered.length; i++) {
+            if (mStripTabsVisuallyOrdered[i] == tab) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    /**
+     * @param tab The StripLayoutTab you're looking at.
+     * @return Whether or not this tab is the foreground tab.
+     */
+    @VisibleForTesting
+    public boolean isForegroundTab(StripLayoutTab tab) {
+        return tab == mStripTabsVisuallyOrdered[mStripTabsVisuallyOrdered.length - 1];
+    }
+
+    private void startReorderMode(long time, float currentX, float startX) {
+        if (mInReorderMode) return;
+
+        // 1. Reset the last pressed close button state.
+        if (mLastPressedCloseButton != null && mLastPressedCloseButton.isPressed()) {
+            mLastPressedCloseButton.setPressed(false);
+        }
+        mLastPressedCloseButton = null;
+
+        // 2. Check to see if we have a valid tab to start dragging.
+        mInteractingTab = getTabAtPosition(startX);
+        if (mInteractingTab == null) return;
+
+        // 3. Set initial state parameters.
+        mLastReorderScrollTime = 0;
+        mReorderState = REORDER_SCROLL_NONE;
+        mLastReorderX = startX;
+        mInReorderMode = true;
+
+        // 4. Select this tab so that it is always in the foreground.
+        TabModelUtils.setIndex(
+                mModel, TabModelUtils.getTabIndexById(mModel, mInteractingTab.getId()));
+
+        // 5. Fast expand to make sure this tab is visible.
+        float fastExpandDelta = calculateOffsetToMakeTabVisible(mInteractingTab, true, true, true);
+        mScroller.startScroll(mScrollOffset, 0, (int) fastExpandDelta, 0, time, EXPAND_DURATION_MS);
+
+        // 6. Request an update.
+        mUpdateHost.requestUpdate();
+    }
+
+    private void stopReorderMode() {
+        if (!mInReorderMode) return;
+
+        // 1. Reset the state variables.
+        mLastReorderScrollTime = 0;
+        mReorderState = REORDER_SCROLL_NONE;
+        mLastReorderX = 0.f;
+        mInReorderMode = false;
+
+        // 2. Clear any drag offset.
+        startAnimation(buildTabMoveAnimation(mInteractingTab, mInteractingTab.getOffsetX()), true);
+
+        // 3. Request an update.
+        mUpdateHost.requestUpdate();
+    }
+
+    private void updateReorderPosition(float deltaX) {
+        if (!mInReorderMode || mInteractingTab == null) return;
+
+        float offset = mInteractingTab.getOffsetX() + deltaX;
+        int curIndex = findIndexForTab(mInteractingTab.getId());
+
+        // 1. Compute the reorder threshold values.
+        final float flipWidth = mCachedTabWidth - mTabOverlapWidth;
+        final float flipThreshold = REORDER_OVERLAP_SWITCH_PERCENTAGE * flipWidth;
+
+        // 2. Check if we should swap tabs and track the new destination index.
+        int destIndex = TabModel.INVALID_TAB_INDEX;
+        boolean pastLeftThreshold = offset < -flipThreshold;
+        boolean pastRightThreshold = offset > flipThreshold;
+        boolean isNotRightMost = curIndex < mStripTabs.length - 1;
+        boolean isNotLeftMost = curIndex > 0;
+
+        if (LocalizationUtils.isLayoutRtl()) {
+            boolean oldLeft = pastLeftThreshold;
+            pastLeftThreshold = pastRightThreshold;
+            pastRightThreshold = oldLeft;
+        }
+
+        if (pastRightThreshold && isNotRightMost) {
+            destIndex = curIndex + 2;
+        } else if (pastLeftThreshold && isNotLeftMost) {
+            destIndex = curIndex - 1;
+        }
+
+        // 3. If we should swap tabs, make the swap.
+        if (destIndex != TabModel.INVALID_TAB_INDEX) {
+            // 3.a. Since we're about to move the tab we're dragging, adjust it's offset so it
+            // stays in the same apparent position.
+            boolean shouldFlip =
+                    LocalizationUtils.isLayoutRtl() ? destIndex < curIndex : destIndex > curIndex;
+            offset += MathUtils.flipSignIf(flipWidth, shouldFlip);
+
+            // 3.b. Swap the tabs.
+            reorderTab(mInteractingTab.getId(), curIndex, destIndex, true);
+            mModel.moveTab(mInteractingTab.getId(), destIndex);
+
+            // 3.c. Update our curIndex as we have just moved the tab.
+            curIndex += destIndex > curIndex ? 1 : -1;
+
+            // 3.d. Update visual tab ordering.
+            updateVisualTabOrdering();
+        }
+
+        // 4. Limit offset based on tab position.  First tab can't drag left, last tab can't drag
+        // right.
+        if (curIndex == 0) {
+            offset =
+                    LocalizationUtils.isLayoutRtl() ? Math.min(0.f, offset) : Math.max(0.f, offset);
+        }
+        if (curIndex == mStripTabs.length - 1) {
+            offset =
+                    LocalizationUtils.isLayoutRtl() ? Math.max(0.f, offset) : Math.min(0.f, offset);
+        }
+
+        // 5. Set the new offset.
+        mInteractingTab.setOffsetX(offset);
+    }
+
+    private void reorderTab(int id, int oldIndex, int newIndex, boolean animate) {
+        StripLayoutTab tab = findTabById(id);
+        if (tab == null || oldIndex == newIndex) return;
+
+        // 1. If the tab is already at the right spot, don't do anything.
+        int index = findIndexForTab(id);
+        if (index == newIndex) return;
+
+        // 2. Check if it's the tab we are dragging, but we have an old source index.  Ignore in
+        // this case because we probably just already moved it.
+        if (mInReorderMode && index != oldIndex && tab == mInteractingTab) return;
+
+        // 3. Swap the tabs.
+        moveElement(mStripTabs, index, newIndex);
+
+        // 4. Update newIndex to point to the proper element.
+        if (index < newIndex) newIndex--;
+
+        // 5. Animate if necessary.
+        if (animate) {
+            final float flipWidth = mCachedTabWidth - mTabOverlapWidth;
+            final int direction = oldIndex <= newIndex ? 1 : -1;
+            final float animationLength =
+                    MathUtils.flipSignIf(direction * flipWidth, LocalizationUtils.isLayoutRtl());
+            StripLayoutTab slideTab = mStripTabs[newIndex - direction];
+            startAnimation(buildTabMoveAnimation(slideTab, animationLength), true);
+        }
+    }
+
+    private void handleReorderAutoScrolling(long time) {
+        if (!mInReorderMode) return;
+
+        // 1. Track the delta time since the last auto scroll.
+        final float deltaSec =
+                mLastReorderScrollTime == 0 ? 0.f : (time - mLastReorderScrollTime) / 1000.f;
+        mLastReorderScrollTime = time;
+
+        final float x = mInteractingTab.getDrawX();
+
+        // 2. Calculate the gutters for accelerating the scroll speed.
+        // Speed: MAX    MIN                  MIN    MAX
+        // |-------|======|--------------------|======|-------|
+        final float dragRange = REORDER_EDGE_SCROLL_START_MAX_DP - REORDER_EDGE_SCROLL_START_MIN_DP;
+        final float leftMinX = REORDER_EDGE_SCROLL_START_MIN_DP + mLeftMargin;
+        final float leftMaxX = REORDER_EDGE_SCROLL_START_MAX_DP + mLeftMargin;
+        final float rightMinX =
+                mWidth - mLeftMargin - mRightMargin - REORDER_EDGE_SCROLL_START_MIN_DP;
+        final float rightMaxX =
+                mWidth - mLeftMargin - mRightMargin - REORDER_EDGE_SCROLL_START_MAX_DP;
+
+        // 3. See if the current draw position is in one of the gutters and figure out how far in.
+        // Note that we only allow scrolling in each direction if the user has already manually
+        // moved that way.
+        float dragSpeedRatio = 0.f;
+        if ((mReorderState & REORDER_SCROLL_LEFT) != 0 && x < leftMinX) {
+            dragSpeedRatio = -(leftMinX - Math.max(x, leftMaxX)) / dragRange;
+        } else if ((mReorderState & REORDER_SCROLL_RIGHT) != 0 && x + mCachedTabWidth > rightMinX) {
+            dragSpeedRatio = (Math.min(x + mCachedTabWidth, rightMaxX) - rightMinX) / dragRange;
+        }
+
+        dragSpeedRatio = MathUtils.flipSignIf(dragSpeedRatio, LocalizationUtils.isLayoutRtl());
+
+        if (dragSpeedRatio != 0.f) {
+            // 4.a. We're in a gutter.  Update the scroll offset.
+            float dragSpeed = REORDER_EDGE_SCROLL_MAX_SPEED_DP * dragSpeedRatio;
+            updateScrollOffsetPosition((int) (mScrollOffset + dragSpeed * deltaSec));
+
+            mUpdateHost.requestUpdate();
+        } else {
+            // 4.b. We're not in a gutter.  Reset the scroll delta time tracker.
+            mLastReorderScrollTime = 0;
+        }
+    }
+
+    private void resetResizeTimeout(boolean postIfNotPresent) {
+        final boolean present = mStripTabEventHandler.hasMessages(MESSAGE_RESIZE);
+
+        if (present) mStripTabEventHandler.removeMessages(MESSAGE_RESIZE);
+
+        if (present || postIfNotPresent) {
+            mStripTabEventHandler.sendEmptyMessageAtTime(MESSAGE_RESIZE, RESIZE_DELAY_MS);
+        }
+    }
+
+    private class StripTabEventHandler extends Handler {
+        @Override
+        public void handleMessage(Message m) {
+            switch (m.what) {
+                case MESSAGE_RESIZE:
+                    computeAndUpdateTabWidth(true);
+                    mUpdateHost.requestUpdate();
+                    break;
+                case MESSAGE_UPDATE_SPINNER:
+                    mUpdateHost.requestUpdate();
+                    break;
+                default:
+                    assert false : "StripTabEventHandler got unknown message " + m.what;
+            }
+        }
+    }
+
+    private class TabLoadTrackerCallbackImpl implements TabLoadTrackerCallback {
+        @Override
+        public void loadStateChanged(int id) {
+            mUpdateHost.requestUpdate();
+        }
+    }
+
+    private static Animation<Animatable<?>> buildTabCreatedAnimation(StripLayoutTab tab) {
+        return createAnimation(tab, StripLayoutTab.Property.Y_OFFSET, tab.getHeight(), 0.f,
+                ANIM_TAB_CREATED_MS, 0, false, ChromeAnimation.getLinearInterpolator());
+    }
+
+    private static Animation<Animatable<?>> buildTabClosedAnimation(StripLayoutTab tab) {
+        return createAnimation(tab, StripLayoutTab.Property.Y_OFFSET, tab.getOffsetY(),
+                tab.getHeight(), ANIM_TAB_CLOSED_MS, 0, false,
+                ChromeAnimation.getLinearInterpolator());
+    }
+
+    private static Animation<Animatable<?>> buildTabResizeAnimation(
+            StripLayoutTab tab, float width) {
+        return createAnimation(tab, StripLayoutTab.Property.WIDTH, tab.getWidth(), width,
+                ANIM_TAB_RESIZE_MS, 0, false, ChromeAnimation.getLinearInterpolator());
+    }
+
+    private static Animation<Animatable<?>> buildTabMoveAnimation(
+            StripLayoutTab tab, float startX) {
+        return createAnimation(tab, StripLayoutTab.Property.X_OFFSET, startX, 0.f, ANIM_TAB_MOVE_MS,
+                0, false, ChromeAnimation.getLinearInterpolator());
+    }
+
+    private static <T> void moveElement(T[] array, int oldIndex, int newIndex) {
+        if (oldIndex <= newIndex) {
+            moveElementUp(array, oldIndex, newIndex);
+        } else {
+            moveElementDown(array, oldIndex, newIndex);
+        }
+    }
+
+    private static <T> void moveElementUp(T[] array, int oldIndex, int newIndex) {
+        assert oldIndex <= newIndex;
+        if (oldIndex == newIndex || oldIndex + 1 == newIndex) return;
+
+        T elem = array[oldIndex];
+        for (int i = oldIndex; i < newIndex - 1; i++) {
+            array[i] = array[i + 1];
+        }
+        array[newIndex - 1] = elem;
+    }
+
+    private static <T> void moveElementDown(T[] array, int oldIndex, int newIndex) {
+        assert oldIndex >= newIndex;
+        if (oldIndex == newIndex) return;
+
+        T elem = array[oldIndex];
+        for (int i = oldIndex - 1; i >= newIndex; i--) {
+            array[i + 1] = array[i];
+        }
+        array[newIndex] = elem;
+    }
+
+    /**
+     * Sets the current scroll offset of the TabStrip.
+     * @param offset The offset to set the TabStrip's scroll state to.
+     */
+    @VisibleForTesting
+    public void testSetScrollOffset(int offset) {
+        mScrollOffset = offset;
+    }
+
+    /**
+     * Starts a fling with the specified velocity.
+     * @param velocity The velocity to trigger the fling with.  Negative to go left, positive to go
+     * right.
+     */
+    @VisibleForTesting
+    public void testFling(float velocity) {
+        fling(SystemClock.uptimeMillis(), 0, 0, velocity, 0);
+    }
+
+    /**
+     * Displays the tab menu below the anchor tab.
+     * @param anchorTab The tab the menu will be anchored to
+     */
+    private void showTabMenu(StripLayoutTab anchorTab) {
+        // 1. Bring the anchor tab to the foreground.
+        int tabIndex = TabModelUtils.getTabIndexById(mModel, anchorTab.getId());
+        TabModelUtils.setIndex(mModel, tabIndex);
+
+        // 2. Anchor the popupMenu to the view associated with the tab
+        View tabView = TabModelUtils.getCurrentTab(mModel).getView();
+        mTabMenu.setAnchorView(tabView);
+
+        // 3. Set the vertical offset to align the tab menu with bottom of the tab strip
+        int verticalOffset =
+                -(tabView.getHeight()
+                        - (int) mContext.getResources().getDimension(R.dimen.tab_strip_height));
+        mTabMenu.setVerticalOffset(verticalOffset);
+
+        // 4. Set the horizontal offset to align the tab menu with the right side of the tab
+        int horizontalOffset = Math.round((anchorTab.getDrawX() + anchorTab.getWidth())
+                                       * mContext.getResources().getDisplayMetrics().density)
+                - mTabMenu.getWidth();
+        mTabMenu.setHorizontalOffset(horizontalOffset);
+
+        mTabMenu.show();
+    }
+
+    /**
+     * @return true if the tab menu is showing
+     */
+    @VisibleForTesting
+    public boolean isTabMenuShowing() {
+        return mTabMenu.isShowing();
+    }
+
+    /**
+     * @param menuItemId The id of the menu item to click
+     */
+    @VisibleForTesting
+    public void clickTabMenuItem(int menuItemId) {
+        mTabMenu.performItemClick(menuItemId);
+    }
+}