[Reland] [Extensions] Make extension message bubble factory platform-abstract

chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm

Index: chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
diff --git a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
index dc640a18c3ed719ee9875e8defca806e81fa2b57..19f9ac8aea7d2423ded80b52a3906d777e4384cc 100644
--- a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
@@ -171,6 +171,9 @@ class ToolbarActionsBarBridge : public ToolbarActionsBarDelegate {
   bool IsPopupRunning() const override;
   void OnOverflowedActionWantsToRunChanged(bool overflowed_action_wants_to_run)
       override;
+  void ShowExtensionMessageBubble(
+      scoped_ptr<extensions::ExtensionMessageBubbleController> controller)
+          override;
 
   // The owning BrowserActionsController; weak.
   BrowserActionsController* controller_;
@@ -248,6 +251,11 @@ void ToolbarActionsBarBridge::OnOverflowedActionWantsToRunChanged(
       setOverflowedToolbarActionWantsToRun:overflowed_action_wants_to_run];
 }
 
+void ToolbarActionsBarBridge::ShowExtensionMessageBubble(
+    scoped_ptr<extensions::ExtensionMessageBubbleController> controller) {
+  NOTREACHED();  // Not yet implemented on Mac.
+}
+
 }  // namespace
 
 @implementation BrowserActionsController