Fix the issue that GetFrameWindow() may change between AddObserver and RemoveObserver in KeyboardCo…

ui/keyboard/keyboard_controller.h

Index: ui/keyboard/keyboard_controller.h
diff --git a/ui/keyboard/keyboard_controller.h b/ui/keyboard/keyboard_controller.h
index 492a0ca00650981f9f7e3600cec9c34008cdbe78..49dfc6592dc97ee5f59b30e150e499c0991f2566 100644
--- a/ui/keyboard/keyboard_controller.h
+++ b/ui/keyboard/keyboard_controller.h
@@ -5,6 +5,8 @@
 #ifndef UI_KEYBOARD_KEYBOARD_CONTROLLER_H_
 #define UI_KEYBOARD_KEYBOARD_CONTROLLER_H_
 
+#include <set>
+
 #include "base/basictypes.h"
 #include "base/event_types.h"
 #include "base/memory/scoped_ptr.h"
@@ -153,6 +155,8 @@ class KEYBOARD_EXPORT KeyboardController : public ui::InputMethodObserver,
 
   scoped_ptr<WindowBoundsChangeObserver> window_bounds_observer_;
 
+  std::set<aura::Window*> observed_windows_;
+
   ui::InputMethod* input_method_;
   bool keyboard_visible_;
   bool show_on_resize_;