[WebView] Move external video surface across container views.

content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java

Index: content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
index d0ac836bf30b8771f9f217e6664c4d219ed7e02d..1aba5bba6b1015a8737ac533d0a4db7fc94b94d2 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ContentViewCore.java
@@ -485,6 +485,7 @@ public class ContentViewCore
     private ViewAndroid mViewAndroid;
 
     private SmartClipDataListener mSmartClipDataListener = null;
+    private ObserverList<ContainerViewObserver> mContainerViewObservers;
 
     // This holds the state of editable text (e.g. contents of <input>, contenteditable) of
     // a focused element.
@@ -544,6 +545,7 @@ public class ContentViewCore
 
         mEditable = Editable.Factory.getInstance().newEditable("");
         Selection.setSelection(mEditable, 0);
+        mContainerViewObservers = new ObserverList<ContainerViewObserver>();
     }
 
     /**
@@ -815,11 +817,22 @@ public class ContentViewCore
             mContainerView.setWillNotDraw(false); // TODO(epenner): Remove (http://crbug.com/436689)
             mContainerView.setClickable(true);
             mViewAndroidDelegate.updateCurrentContainerView();
+            for (ContainerViewObserver observer : mContainerViewObservers) {
+                observer.onContainerViewChanged(mContainerView);
+            }
         } finally {
             TraceEvent.end("ContentViewCore.setContainerView");
         }
     }
 
+    public void addContainerViewObserver(ContainerViewObserver observer) {
+        mContainerViewObservers.addObserver(observer);
+    }
+
+    public void removeContainerViewObserver(ContainerViewObserver observer) {
+        mContainerViewObservers.removeObserver(observer);
+    }
+
     @CalledByNative
     void onNativeContentViewCoreDestroyed(long nativeContentViewCore) {
         assert nativeContentViewCore == mNativeContentViewCore;
@@ -930,6 +943,7 @@ public class ContentViewCore
         mGestureStateListeners.clear();
         ScreenOrientationListener.getInstance().removeObserver(this);
         mPositionObserver.clearListener();
+        mContainerViewObservers.clear();
     }
 
     private void unregisterAccessibilityContentObserver() {