mus: Fix handled status in UI event ack, add MessageLoop::NestingObserver

ui/views/mus/platform_window_mus.h

 // 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.
 
 #ifndef UI_VIEWS_MUS_PLATFORM_WINDOW_MUS_H_
 #define UI_VIEWS_MUS_PLATFORM_WINDOW_MUS_H_
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "components/mus/public/cpp/input_event_handler.h"
 #include "components/mus/public/cpp/window_observer.h"
 #include "ui/platform_window/platform_window.h"
 #include "ui/views/mus/mus_export.h"
 
 namespace bitmap_uploader {
 class BitmapUploader;
 }
 
 namespace shell {
 class Connector;
 }
 
 namespace ui {
 class Event;
 class ViewProp;
 }
 
 namespace views {
 
 class VIEWS_MUS_EXPORT PlatformWindowMus
     : public NON_EXPORTED_BASE(ui::PlatformWindow),
       public mus::WindowObserver,
-      public NON_EXPORTED_BASE(mus::InputEventHandler) {
+      public NON_EXPORTED_BASE(mus::InputEventHandler),
+      public base::MessageLoop::NestingObserver {
  public:
   PlatformWindowMus(ui::PlatformWindowDelegate* delegate,
                     shell::Connector* connector,
                     mus::Window* mus_window);
   ~PlatformWindowMus() override;
 
   void Activate();
 
   void SetCursorById(mus::mojom::Cursor cursor);
 
@@ skipping 34 matching lines @@
       const std::vector<uint8_t>* new_data) override;
   void OnRequestClose(mus::Window* window) override;
 
   // mus::InputEventHandler:
   void OnWindowInputEvent(
       mus::Window* view,
       const ui::Event& event,
       std::unique_ptr<base::Callback<void(mus::mojom::EventResult)>>*
           ack_callback) override;
 
+  // base::MessageLoop::NestingObserver:
+  void OnBeginNestedMessageLoop() override;
+
   ui::PlatformWindowDelegate* delegate_;
   mus::Window* mus_window_;
   mus::mojom::ShowState show_state_;
   mus::mojom::Cursor last_cursor_;
 
+  std::unique_ptr<base::Callback<void(mus::mojom::EventResult)>>
+      event_ack_callback_;
+
   // True if OnWindowDestroyed() has been received.
   bool mus_window_destroyed_;
 
   std::unique_ptr<bitmap_uploader::BitmapUploader> bitmap_uploader_;
   std::unique_ptr<ui::ViewProp> prop_;
 #ifndef NDEBUG
   std::unique_ptr<base::WeakPtrFactory<PlatformWindowMus>> weak_factory_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PlatformWindowMus);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_PLATFORM_WINDOW_MUS_H_