Add/remove surface references via MojoCompositorFrameSink.

services/ui/ws/server_window_delegate.h

 // Copyright 2014 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 SERVICES_UI_WS_SERVER_WINDOW_DELEGATE_H_
 #define SERVICES_UI_WS_SERVER_WINDOW_DELEGATE_H_
 
 #include <memory>
 
 #include "services/ui/public/interfaces/mus_constants.mojom.h"
@@ skipping 13 matching lines @@
 struct ClientWindowId;
 class ServerWindow;
 struct WindowId;
 
 class ServerWindowDelegate {
  public:
   // Returns a display compositor interface pointer. There is only one
   // DisplayCompositor running in the system.
   virtual cc::mojom::DisplayCompositor* GetDisplayCompositor() = 0;
 
+  virtual const cc::SurfaceId& GetRootSurfaceId() const = 0;
+
   // Returns the root of the window tree to which this |window| is attached.
   // Returns null if this window is not attached up through to a root window.
   virtual ServerWindow* GetRootWindow(const ServerWindow* window) = 0;
 
  protected:
   virtual ~ServerWindowDelegate() {}
 };
 
 }  // namespace ws
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_WS_SERVER_WINDOW_DELEGATE_H_