mash: Don't close system tray bubble for clicks in menus/notifications

mash/wm/root_window_controller.cc

Index: mash/wm/root_window_controller.cc
diff --git a/mash/wm/root_window_controller.cc b/mash/wm/root_window_controller.cc
index f2dc0734fead9a65aa678e835e087d857b1f27bb..582f2429a9980a583eac02b942eec9003f2a4bf3 100644
--- a/mash/wm/root_window_controller.cc
+++ b/mash/wm/root_window_controller.cc
@@ -165,7 +165,8 @@ void RootWindowController::OnConnectionLost(
   delete this;
 }
 
-void RootWindowController::OnEventObserved(const ui::Event& event) {
+void RootWindowController::OnEventObserved(const ui::Event& event,
+                                           mus::Window* target) {
   // Does not use EventObservers.
 }