mus: Embedder can request and observe BeginFrame for embedded client.

ui/aura/window.h

 // Copyright (c) 2012 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_AURA_WINDOW_H_
 #define UI_AURA_WINDOW_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 296 matching lines @@
 
   // Returns true if there was state needing to be cleaned up.
   bool CleanupGestureState();
 
   // Create a CompositorFrameSink for the aura::Window.
   std::unique_ptr<cc::CompositorFrameSink> CreateCompositorFrameSink();
 
   // Get the current cc::SurfaceId.
   cc::SurfaceId GetSurfaceId() const;
 
+  // See documentation for WindowPort::SetNeedsBeginFrames().
+  void SetNeedsBeginFrames(
+      bool needs,
+      base::RepeatingClosure callback = base::RepeatingClosure());
+
  protected:
   // Deletes (or removes if not owned by parent) all child windows. Intended for
   // use from the destructor.
   void RemoveOrDestroyChildren();
 
   // Overrides from ui::PropertyHandler
   std::unique_ptr<ui::PropertyData> BeforePropertyChange(const void* key)
       override;
   void AfterPropertyChange(const void* key,
                            int64_t old_value,
@@ skipping 155 matching lines @@
   bool ignore_events_;
 
   base::ObserverList<WindowObserver, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_H_