[Extensions UI] Convert ExtensionMessageBubbles to ToolbarActionsBarBubbles

chrome/browser/ui/extensions/extension_message_bubble_bridge.cc

 // 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.
 
 #include "chrome/browser/ui/extensions/extension_message_bubble_bridge.h"
 
 #include <utility>
 
 #include "chrome/browser/extensions/extension_message_bubble_controller.h"
 
@@ skipping 54 matching lines @@
       break;
     }
     case CLOSE_EXECUTE:
       controller_->OnBubbleAction();
       break;
     case CLOSE_LEARN_MORE:
       controller_->OnLinkClicked();
       break;
   }
 }
-
-bool ExtensionMessageBubbleBridge::IsExtensionMessageBubble() {
-  return true;
-}