WIP: Eliminate event.target() usage from TrayEventFilter

mash/wm/root_window_controller.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mash/wm/root_window_controller.h"
 
 #include <stdint.h>
 
 #include "base/bind.h"
 #include "components/mus/common/util.h"
@@ skipping 147 matching lines @@
 
   app_->OnRootWindowControllerDoneInit(this);
 }
 
 void RootWindowController::OnConnectionLost(
     mus::WindowTreeConnection* connection) {
   shadow_controller_.reset();
   delete this;
 }
 
-void RootWindowController::OnEventObserved(const ui::Event& event) {
+void RootWindowController::OnEventObserved(const ui::Event& event,
+                                           mus::Window* target) {
   // Does not use EventObservers.
 }
 
 void RootWindowController::OnWindowDestroyed(mus::Window* window) {
   DCHECK_EQ(window, root_);
   app_->OnRootWindowDestroyed(this);
   root_->RemoveObserver(this);
   // Delete the |window_manager_| here so that WindowManager doesn't have to
   // worry about the possibility of |root_| being null.
   window_manager_.reset();
@@ skipping 37 matching lines @@
   CreateContainer(mojom::Container::BUBBLES, mojom::Container::ROOT);
   CreateContainer(mojom::Container::SYSTEM_MODAL_WINDOWS,
                   mojom::Container::ROOT);
   CreateContainer(mojom::Container::KEYBOARD, mojom::Container::ROOT);
   CreateContainer(mojom::Container::MENUS, mojom::Container::ROOT);
   CreateContainer(mojom::Container::TOOLTIPS, mojom::Container::ROOT);
 }
 
 }  // namespace wm
 }  // namespace mash