Upstream oodles of Chrome for Android code into Chromium.

chrome/android/java_staging/src/org/chromium/chrome/browser/ntp/RecentTabsExpandableListView.java

+// 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.ntp;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.View;
+import android.widget.ExpandableListView;
+
+import org.chromium.ui.base.DeviceFormFactor;
+
+/**
+ * Customized ExpandableListView for the recent tabs page. This class handles tablet-specific
+ * layout implementation.
+ */
+public class RecentTabsExpandableListView extends ExpandableListView {
+    private static final int MAX_LIST_VIEW_WIDTH_DP = 550;
+
+    private int mMaxListViewWidth;
+    private int mSavedListPosition = 0;
+    private int mSavedListTop = 0;
+
+    /**
+     * Constructor for inflating from XML.
+     */
+    public RecentTabsExpandableListView(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    @Override
+    protected void onFinishInflate() {
+        super.onFinishInflate();
+        float density = getResources().getDisplayMetrics().density;
+        mMaxListViewWidth = Math.round(MAX_LIST_VIEW_WIDTH_DP * density);
+    }
+
+    @Override
+    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        if (!DeviceFormFactor.isTablet(getContext())) {
+            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+            return;
+        }
+
+        // Increase padding if needed to ensure children are no wider than mMaxListViewWidth.
+        int childWidth = MeasureSpec.getSize(widthMeasureSpec);
+        int excessWidth = childWidth - mMaxListViewWidth;
+        int horizontalPadding = 0;
+        if (excessWidth > 0) {
+            horizontalPadding += excessWidth / 2;
+        }
+
+        setPadding(horizontalPadding, 0, horizontalPadding, 0);
+
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+    }
+
+    @Override
+    protected void onAttachedToWindow() {
+        super.onAttachedToWindow();
+        setSelectionFromTop(mSavedListPosition, mSavedListTop);
+    }
+
+    @Override
+    protected void onDetachedFromWindow() {
+        mSavedListPosition = getFirstVisiblePosition();
+        View v = getChildAt(0);
+        mSavedListTop = (v == null) ? 0 : v.getTop();
+        super.onDetachedFromWindow();
+    }
+}