Prevent mouse from getting stuck on second display in login

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 920c553c28fcae8f89f49bf8c6fb7c57863a012a..b3ffd5816759d94abc7642624442c75d4cc999d8 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -240,6 +240,13 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
   // The shelf for managing the launcher and the status widget.
   scoped_ptr<ShelfWidget> shelf_;
 
+  // An invisible/empty window used as a event target for
+  // |MouseCursorEventFilter| before a user logs in.
+  // (crbug.com/266987)
+  // Its container is |LockScreenBackgroundContainer| and
+  // this must be deleted before the container is deleted.
+  scoped_ptr<aura::Window> mouse_event_target_;
+
   // Manages layout of docked windows. Owned by DockedContainer.
   DockedWindowLayoutManager* docked_layout_manager_;