Do not send the OnWindowShowTypeChanged() notification if the show type has not changed

ash/wm/window_state.h

Index: ash/wm/window_state.h
diff --git a/ash/wm/window_state.h b/ash/wm/window_state.h
index 4bcacc3845aa9243afa0bc2e6c09bddb43004b4f..618349c86d61678619524c48f6b645f7b83249f0 100644
--- a/ash/wm/window_state.h
+++ b/ash/wm/window_state.h
@@ -254,6 +254,9 @@ class ASH_EXPORT WindowState : public aura::WindowObserver {
   void SnapWindow(WindowShowType left_or_right,
                   const gfx::Rect& bounds);
 
+  // Sets the window show type and updates the show state if necessary.
+  void SetWindowShowType(WindowShowType new_window_show_type);
+
   // The owner of this window settings.
   aura::Window* window_;
   scoped_ptr<WindowStateDelegate> delegate_;
@@ -279,6 +282,9 @@ class ASH_EXPORT WindowState : public aura::WindowObserver {
 
   ObserverList<WindowStateObserver> observer_list_;
 
+  // True when in SetWindowShowType(). This is used to avoid reentrance.
+  bool in_set_window_show_type_;
+
   WindowShowType window_show_type_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowState);