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

ui/keyboard/keyboard_controller.cc

Index: ui/keyboard/keyboard_controller.cc
diff --git a/ui/keyboard/keyboard_controller.cc b/ui/keyboard/keyboard_controller.cc
index ceef5941f7e424a9e912a7ad8ee0f8fe9ff73751..801c68ca5910a7a027e125ca05e26d346bf9fff5 100644
--- a/ui/keyboard/keyboard_controller.cc
+++ b/ui/keyboard/keyboard_controller.cc
@@ -143,11 +143,9 @@ void ToggleTouchEventLogging(bool enable) {
 }
 
 aura::Window *GetFrameWindow(aura::Window *window) {
-  // Each container window has a non-negative id.  Stop traversing at the child
-  // of a container window.
   if (!window)
     return NULL;
-  while(window->parent() && window->parent()->id() < 0) {

[Shu Chen, 2014/09/02 04:43:42]

Kevin/Biao, do you think there is a case that a top Window had a negative id?

I've tested this change a little bit on linux_chromeos and cannot find any
problems.

If you think it'd better to be safe to check negative id here, an alternative
solution is to hold a set of "observed windows", and make sure RemoveObserver()
on all "observed windows" at destructor.

The crash bug was caused by
https://code.google.com/p/chromium/codesearch#chromium/src/ui/aura/window_obs....

[bshe, 2014/09/02 12:58:47]

I am not familiar with this code. kevers@ could comment better.

But it seems like the new code returns the top level window, while the old code
returns the immediate child of top level window if I am reading it correctly. I
am a little bit nervous about this change but I dont know enough to be certain.

[Shu Chen, 2014/09/02 14:30:43]

Done. I've changed to safer solution.

+  while(window->parent()) {
     window = window->parent();
   }
   return window;