Add ability for a BubbleReference to update the BubbleUI.

components/bubble/bubble_delegate.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_BUBBLE_BUBBLE_DELEGATE_H_
 #define COMPONENTS_BUBBLE_BUBBLE_DELEGATE_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "components/bubble/bubble_close_reason.h"
 
 class BubbleUI;
 
 // Inherit from this class to define a bubble. A bubble is a small transient UI
 // surface anchored to a parent window. Most bubbles are dismissed when they
 // lose focus.
 class BubbleDelegate {
  public:
   BubbleDelegate();
   virtual ~BubbleDelegate();
 
   // Called by BubbleController to notify a bubble of an event that the bubble
   // might want to close on. Return true if the bubble should close for the
   // specified reason.
   virtual bool ShouldClose(BubbleCloseReason reason);
 
   // Called by BubbleController to build the UI that will represent this bubble.
   // BubbleDelegate should not keep a reference to this newly created UI.
   virtual scoped_ptr<BubbleUI> BuildBubbleUI() = 0;
 
+  // Called to update an existing UI. This is the same BubbleUI that was created
+  // in |BuildBubbleUI|.
+  // Return true to indicate the UI was updated.
+  virtual bool UpdateBubbleUI(BubbleUI* bubble_ui);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(BubbleDelegate);
 };
 
 #endif  // COMPONENTS_BUBBLE_BUBBLE_DELEGATE_H_