Fix crash which occurs when a widget destroys itself as a result of ET_GESTURE_TAP_DOWN

ash/wm/caption_buttons/frame_maximize_button.h

 // Copyright 2013 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 ASH_WM_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_H_
 #define ASH_WM_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_H_
 
 #include "ash/ash_export.h"
 #include "ash/wm/caption_buttons/caption_button_types.h"
 #include "ash/wm/caption_buttons/frame_caption_button.h"
+#include "ash/wm/window_state_observer.h"
 #include "ash/wm/workspace/snap_types.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/timer/timer.h"
 #include "ui/aura/window_observer.h"
 #include "ui/views/widget/widget_observer.h"
 
 namespace views {
 class Widget;
 }
 
 namespace ash {
 class FrameMaximizeButtonObserver;
 
 namespace internal {
 class PhantomWindowController;
 class SnapSizer;
 }
 
 class MaximizeBubbleController;
 
 // Button used for the maximize control on the frame. Handles snapping logic.
 class ASH_EXPORT FrameMaximizeButton : public FrameCaptionButton,
                                        public views::WidgetObserver,
-                                       public aura::WindowObserver {
+                                       public aura::WindowObserver,
+                                       public wm::WindowStateObserver {
  public:
   FrameMaximizeButton(views::ButtonListener* listener,
                       views::Widget* frame);
   virtual ~FrameMaximizeButton();
 
   void AddObserver(FrameMaximizeButtonObserver* observer);
   void RemoveObserver(FrameMaximizeButtonObserver* observer);
 
   // Updates |snap_type_| based on a a given snap type. This is used by
   // external hover events from the button menu.
@@ skipping 14 matching lines @@
 
   // WindowObserver overrides:
   virtual void OnWindowBoundsChanged(aura::Window* window,
                                      const gfx::Rect& old_bounds,
                                      const gfx::Rect& new_bounds) OVERRIDE;
   virtual void OnWindowPropertyChanged(aura::Window* window,
                                        const void* key,
                                        intptr_t old) OVERRIDE;
   virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
 
+  // wm::WindowStateObserver override:
+  virtual void OnPostWindowShowTypeChange(wm::WindowState* window_state,
+                                          wm::WindowShowType old_type) OVERRIDE;
+
   // WidgetObserver overrides:
   virtual void OnWidgetActivationChanged(views::Widget* widget,
                                         bool active) OVERRIDE;
 
   // ImageButton overrides:
   virtual bool OnMousePressed(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseEntered(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseExited(const ui::MouseEvent& event) OVERRIDE;
   virtual bool OnMouseDragged(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const ui::MouseEvent& event) OVERRIDE;
@@ skipping 104 matching lines @@
   int bubble_appearance_delay_ms_;
 
   ObserverList<FrameMaximizeButtonObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameMaximizeButton);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_CAPTION_BUTTONS_FRAME_MAXIMIZE_BUTTON_H_