ash: Fix event processing in modal windows in login/lock screen.

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index f1a09263bca0e0db56489d597c0a60a68492fa2d..3f589934729862089d6f3c836f6a3f42b4a88177 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -57,7 +57,15 @@ class ASH_EXPORT RootWindowController {
     return screen_dimmer_.get();
   }
 
-  SystemModalContainerLayoutManager* GetSystemModalLayoutManager();
+  // Returns the layout-manager for the appropriate modal-container. If the
+  // window is inside the lockscreen modal container, then the layout manager
+  // for that is returned. Otherwise the layout manager for the default modal
+  // container is returned.
+  // If no window is specified (i.e. |window| is NULL), then the lockscreen
+  // modal container is used if the screen is currently locked. Otherwise, the
+  // default modal container is used.
+  SystemModalContainerLayoutManager* GetSystemModalLayoutManager(
+      aura::Window* window);
 
   aura::Window* GetContainer(int container_id);