WIP: Eliminate event.target() usage from TrayEventFilter

ui/views/mus/native_widget_mus.cc

 // Copyright 2015 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 "ui/views/mus/native_widget_mus.h"
 
 #include "base/macros.h"
 #include "base/thread_task_runner_handle.h"
 #include "components/mus/public/cpp/property_type_converters.h"
 #include "components/mus/public/cpp/window.h"
@@ skipping 359 matching lines @@
     NativeWidgetMus* native_widget =
         window->GetLocalProperty(kNativeWidgetMusKey);
     if (native_widget && native_widget->GetWidget()->non_client_view()) {
       native_widget->GetWidget()->non_client_view()->Layout();
       native_widget->GetWidget()->non_client_view()->SchedulePaint();
       native_widget->UpdateClientArea();
     }
   }
 }
 
+// static
+Widget* NativeWidgetMus::GetWidgetForWindow(mus::Window* window) {
+  if (!window)
+    return nullptr;
+  NativeWidgetMus* native_widget = window->GetLocalProperty(kNativeWidgetMusKey);
+  if (!native_widget)
+    return nullptr;
+  return native_widget->GetWidget();
+}
+
 aura::Window* NativeWidgetMus::GetRootWindow() {
   return window_tree_host_->window();
 }
 
 void NativeWidgetMus::OnPlatformWindowClosed() {
   native_widget_delegate_->OnNativeWidgetDestroying();
 
   window_tree_client_.reset();  // Uses |content_|.
   capture_client_.reset();      // Uses |content_|.
 
@@ skipping 731 matching lines @@
     window_tree_host_->Show();
     GetNativeWindow()->Show();
   } else {
     window_tree_host_->Hide();
     GetNativeWindow()->Hide();
   }
   native_widget_delegate_->OnNativeWidgetVisibilityChanged(window->visible());
 }
 
 }  // namespace views