[Android] Fix a flicker in stopping Chrome

chrome/android/java/src/org/chromium/chrome/browser/Tab.java

 // Copyright 2014 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;
 
 import android.app.Activity;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.Color;
+import android.os.Handler;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.ContextMenu;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.view.ViewGroup;
 import android.view.ViewGroup.LayoutParams;
 import android.widget.FrameLayout;
 
 import org.chromium.base.CalledByNative;
@@ skipping 243 matching lines @@
     private float mPreviousFullscreenTopControlsOffsetY = Float.NaN;
     private float mPreviousFullscreenContentOffsetY = Float.NaN;
     private float mPreviousFullscreenOverdrawBottomHeight = Float.NaN;
     private int mFullscreenHungRendererToken = FullscreenManager.INVALID_TOKEN;
 
     /**
      * Reference to the current sadTabView if one is defined.
      */
     private View mSadTabView;
 
+    private boolean mStarted;
+
     /**
      * A default {@link ChromeContextMenuItemDelegate} that supports some of the context menu
      * functionality.
      */
     protected class TabChromeContextMenuItemDelegate
             extends EmptyChromeContextMenuItemDelegate {
         private final Clipboard mClipboard;
 
         /**
          * Builds a {@link TabChromeContextMenuItemDelegate} instance.
@@ skipping 774 matching lines @@
             // We can't set a null client, but we should clear references to the last one.
             mContentViewCore.setContentViewClient(new ContentViewClient());
         }
     }
 
     /**
      * Called on the foreground tab when the Activity showing the Tab gets started. This is called
      * on both cold and warm starts.
      */
     public void onActivityStart() {
+        mStarted = true;
         show(TabSelectionType.FROM_USER);
 
         // When resuming the activity, force an update to the fullscreen state to ensure a
         // subactivity did not change the fullscreen configuration of this ChromeTab's renderer in
         // the case where it was shared (i.e. via an EmbedContentViewActivity).
         updateFullscreenEnabledState();
     }
 
     /**
      * Called on the foreground tab when the Activity is stopped.
      */
     public void onActivityStop() {
-        hide();
+        // Delay hiding in order to avoid a white flicker in closing an activity.
+        mStarted = false;
+        final Handler handler = new Handler();
+        handler.postDelayed(new Runnable() {
+            @Override
+            public void run() {
+                if (!mStarted) hide();
+            }
+        }, 500);

[David Trainor- moved to gerrit, 2015/01/09 18:07:52]

Does this only happen on L and above?  Should we only do it on those devices? 
Hmm I wonder if there's a callback for when we actually finish the animation so
we know the exact time to hide.

     }
 
     /**
      * Prepares the tab to be shown. This method is supposed to be called before the tab is
      * displayed. It restores the ContentView if it is not available after the cold start and
      * reloads the tab if its renderer has crashed.
      * @param type Specifies how the tab was selected.
      */
     public final void show(TabSelectionType type) {
         try {
@@ skipping 1262 matching lines @@
             String title);
     private native boolean nativePrint(long nativeTabAndroid);
     private native Bitmap nativeGetFavicon(long nativeTabAndroid);
     private native void nativeCreateHistoricalTab(long nativeTabAndroid);
     private native void nativeUpdateTopControlsState(
             long nativeTabAndroid, int constraints, int current, boolean animate);
     private native void nativeSearchByImageInNewTabAsync(long nativeTabAndroid);
     private native void nativeSetInterceptNavigationDelegate(long nativeTabAndroid,
             InterceptNavigationDelegate delegate);
 }