Add tab reparenting

chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java
index ef5734502a25e32ba4c0c9b2c1e29f7a7409a1f9..9c346bf140bbaae60a7d758ddb24a64db2756ae9 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java
@@ -302,6 +302,15 @@ public class CompositorViewHolder extends FrameLayout
         }
     }
 
+    /**
+     * Perform any initialization necessary for showing a reparented tab.
+     */
+    public void prepareForTabReparenting() {
+        // Set the background to white while we wait for the first swap of buffers. This gets
+        // corrected inside the view.
+        mCompositorView.setBackgroundColor(Color.WHITE);

[Ted C, 2016/02/26 18:46:29]

do we always want white?  or should we use the background color of the page?

[Yusuf, 2016/02/26 19:39:52]

initNative inside CompositorView (which does the same thing for initialization
only) uses WHITE. I think at this point, we may or may not have the background
color from the page yet. For this particular case, at this point, the activity
isn't even aware of the tab it will reparent yet, but knows only that it will
reparent one pretty soon.

[Ted C, 2016/02/26 20:49:36]

Can you reparent with a tab w/ a different background color?  Does this cause
a flicker?

If so, we should figure out a way to get the background color.  This is called
from onStart, which would have the intent if cold start.  Not sure if
onNewIntent
happens before or after onStart.

But if we have the intent then we know the tab id to be reparented and could
get the async params and call tab.getBackgroundColor and pass it in here.

It definitely makes chromeactivity more involved, but we could do something
of the like.

Not needed for this patch though.

+    }
+
     @Override
     public ResourceManager getResourceManager() {
         return mCompositorView.getResourceManager();