Restore focus/activation after the root window has been completely deleted.

ash/display/display_controller.h

Index: ash/display/display_controller.h
diff --git a/ash/display/display_controller.h b/ash/display/display_controller.h
index 53130734ddd55a61b3a3c176e3e99c62de2f8264..ae6e3afe31ff2275583df965e74eabe1cb4e8e39 100644
--- a/ash/display/display_controller.h
+++ b/ash/display/display_controller.h
@@ -31,6 +31,7 @@ template <typename T> class JSONValueConverter;
 namespace ash {
 namespace internal {
 class DisplayManager;
+class FocusActivationStore;
 class RootWindowController;
 }
 
@@ -272,6 +273,8 @@ class ASH_EXPORT DisplayController : public gfx::DisplayObserver {
 
   bool in_bootstrap_;
 
+  scoped_ptr<internal::FocusActivationStore> focus_activation_store_;
+
   DISALLOW_COPY_AND_ASSIGN(DisplayController);
 };