Content: Add convenience method for animations over SurfaceViews.

ui/android/java/src/org/chromium/ui/base/WindowAndroid.java

Index: ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
diff --git a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
index 8f1c58f67ffcf8a7829660e24877662fa70bdd59..0e84cf4ef74d39befa2d5aa3f980d097d91529b0 100644
--- a/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/WindowAndroid.java
@@ -4,6 +4,8 @@
 
 package org.chromium.ui.base;
 
+import android.animation.Animator;
+import android.animation.AnimatorListenerAdapter;
 import android.annotation.SuppressLint;
 import android.app.Activity;
 import android.app.PendingIntent;
@@ -13,6 +15,7 @@ import android.content.Intent;
 import android.os.Bundle;
 import android.util.Log;
 import android.util.SparseArray;
+import android.view.View;
 import android.widget.Toast;
 
 import org.chromium.base.CalledByNative;
@@ -21,6 +24,7 @@ import org.chromium.ui.VSyncMonitor;
 
 import java.lang.ref.WeakReference;
 import java.util.HashMap;
+import java.util.HashSet;
 
 /**
  * The window base class that has the minimum functionality.
@@ -47,6 +51,10 @@ public class WindowAndroid {
     // the Android lint warning "UseSparseArrays".
     protected HashMap<Integer, String> mIntentErrors;
 
+    // We track all animations over content and provide a drawing placeholder for them.
+    private HashSet<Animator> mAnimationsOverContent = new HashSet<Animator>();
+    private View mAnimationPlaceholderView;
+
     private final VSyncMonitor.Listener mVSyncListener = new VSyncMonitor.Listener() {
         @Override
         public void onVSync(VSyncMonitor monitor, long vsyncTimeMicros) {
@@ -289,6 +297,56 @@ public class WindowAndroid {
         return mNativeWindowAndroid;
     }
 
+    /**
+     * Set the animation placeholder view, which we set to 'draw' during animations, such that
+     * animations aren't clipped by the SurfaceView 'hole'. This can be the SurfaceView itself
+     * or a view directly on top of it. This could be extended to many views if we ever need it.
+     */
+    public void setAnimationPlaceholderView(View view) {
+        mAnimationPlaceholderView = view;
+    }
+
+    /**
+     * Start a post-layout animation on top of web content.
+     *
+     * By default, Android optimizes what it shows on top of SurfaceViews (saves power).
+     * Effectively, layouts determine what gets drawn and post-layout animations outside
+     * of this area may be 'clipped'. Using this method to start such animations will
+     * ensure that nothing is clipped during the animation, and restore the optimal
+     * state when the animation ends.
+     */
+    public void startAnimationOverContent(Animator animation) {
+        // We may not need an animation placeholder (eg. Webview doesn't use SurfaceView)
+        if (mAnimationPlaceholderView == null)
+            return;
+        if (animation.isStarted()) throw new IllegalArgumentException("Already started.");
+        boolean added = mAnimationsOverContent.add(animation);
+        if (!added) throw new IllegalArgumentException("Already Added.");
+
+        // We start the animation in this method to help guarantee that we never get stuck in this
+        // state or leak objects into the set. Starting the animation here should guarantee that we
+        // get an onAnimationEnd callback, and remove this animation.
+        animation.start();
+
+        // When the first animation starts, make the placeholder 'draw' itself.
+        if (mAnimationPlaceholderView.willNotDraw()) {
+            mAnimationPlaceholderView.setWillNotDraw(false);
+        }
+
+        // When the last animation ends, remove the placeholder view,
+        // returning to the default optimized state.
+        animation.addListener(new AnimatorListenerAdapter() {
+            @Override
+            public void onAnimationEnd(Animator animation) {
+                animation.removeListener(this);
+                mAnimationsOverContent.remove(animation);
+                if (mAnimationsOverContent.isEmpty()) {
+                    mAnimationPlaceholderView.setWillNotDraw(true);
+                }
+            }
+        });
+    }
+
     private native long nativeInit();
     private native void nativeOnVSync(long nativeWindowAndroid,
                                       long vsyncTimeMicros,