[Extensions Toolbar] Fix action pop out bug and views animation

chrome/browser/ui/toolbar/toolbar_actions_bar_observer.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 CHROME_BROWSER_UI_TOOLBAR_TOOLBAR_ACTIONS_BAR_OBSERVER_H_
+#define CHROME_BROWSER_UI_TOOLBAR_TOOLBAR_ACTIONS_BAR_OBSERVER_H_
+
+class ToolbarActionsBarObserver {
+ public:
+  // Called when the toolbar actions bar is destroyed.
+  virtual void OnToolbarActionsBarDestroyed() {}
+
+  // Called when a toolbar action drag-and-drop sequence has completed.
+  virtual void OnToolbarActionDragDone() {}
+
+  // Called when the toolbar actions bar started to resize (since resizes are
+  // often animated, chances are the bar did not finish resizing).
+  virtual void OnToolbarActionsBarDidStartResize() {}
+
+  virtual ~ToolbarActionsBarObserver() {}
+};
+
+#endif  // CHROME_BROWSER_UI_TOOLBAR_TOOLBAR_ACTIONS_BAR_OBSERVER_H_