Add support for tab migration to DialogSurface

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 f07285b3f08ac05c764048b5942832008cad3829..554ccb19d98d6694892b00c9ddcd04fecdfe09dc 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
@@ -126,6 +126,21 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
         public void updateZoomControls() {}
     };
 
+    /**
+     * Observer for changes to WindowAndroid.  Mirrors
+     * ContentViewCoreImplObserver in native.  Appends 'Android' to (a) match
+     * WindowAndroid, and (b) avoid a name collision with View.
+     */
+    public interface Observer {
+        public void onContentViewCoreDestroyed(ContentViewCore cvc);
+        public void onAttachedToWindowAndroid(ContentViewCore cvc);
+        public void onDetachedFromWindowAndroid(ContentViewCore cvc);
+    }
+
+    // Single observer.  We only support one right now, since we have only one
+    // consumer of it.
+    private Observer mObserver;
+
     // If the embedder adds a JavaScript interface object that contains an indirect reference to
     // the ContentViewCore, then storing a strong ref to the interface object on the native
     // side would prevent garbage collection of the ContentViewCore (as that strong ref would
@@ -905,6 +920,7 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
     private void onNativeContentViewCoreDestroyed(long nativeContentViewCore) {
         assert nativeContentViewCore == mNativeContentViewCore;
         mNativeContentViewCore = 0;
+        if (mObserver != null) mObserver.onContentViewCoreDestroyed(this);
     }
 
     /**
@@ -3463,6 +3479,28 @@ public class ContentViewCore implements AccessibilityStateChangeListener, Screen
         return mShowKeyboardResultReceiver;
     }
 
+    // Set our observer.  We support only a single observer right now.
+    public void addObserver(Observer observer) {
+        assert mObserver == null;
+        mObserver = observer;
+    }
+
+    // Remove our single observer.
+    public void removeObserver(Observer observer) {
+        assert mObserver == observer;
+        mObserver = null;
+    }
+
+    @CalledByNative
+    private void onAttachedToWindowAndroid() {
+        if (mObserver != null) mObserver.onAttachedToWindowAndroid(this);
+    }
+
+    @CalledByNative
+    private void onDetachedFromWindowAndroid() {
+        if (mObserver != null) mObserver.onDetachedFromWindowAndroid(this);
+    }
+
     private native long nativeInit(WebContents webContents, ViewAndroidDelegate viewAndroidDelegate,
             long windowAndroidPtr, HashSet<Object> retainedObjectSet);
     private static native ContentViewCore nativeFromWebContentsAndroid(WebContents webContents);