mojo: Add proper implementation of DetachFromClient to OutputSurfaceMojo.

mojo/cc/output_surface_mojo.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 MOJO_CC_OUTPUT_SURFACE_MOJO_H_
 #define MOJO_CC_OUTPUT_SURFACE_MOJO_H_
 
 #include "base/macros.h"
 #include "cc/output/output_surface.h"
 #include "cc/surfaces/surface_id.h"
 #include "components/mus/public/cpp/view_surface.h"
 #include "components/mus/public/cpp/view_surface_client.h"
 #include "third_party/mojo/src/mojo/public/cpp/bindings/binding.h"
 
 namespace mojo {
 
 class OutputSurfaceMojo : public cc::OutputSurface,
                           public mus::ViewSurfaceClient {
  public:
   OutputSurfaceMojo(const scoped_refptr<cc::ContextProvider>& context_provider,
                     scoped_ptr<mus::ViewSurface> surface);
   ~OutputSurfaceMojo() override;
 
   // cc::OutputSurface implementation.
   void SwapBuffers(cc::CompositorFrame* frame) override;
   bool BindToClient(cc::OutputSurfaceClient* client) override;
+  void DetachFromClient() override;
 
  private:
   // ViewSurfaceClient implementation:
   void OnResourcesReturned(
       mus::ViewSurface* surface,
       mojo::Array<mojo::ReturnedResourcePtr> resources) override;
 
   void SwapBuffersComplete();
 
   scoped_ptr<mus::ViewSurface> surface_;
 
   DISALLOW_COPY_AND_ASSIGN(OutputSurfaceMojo);
 };
 }
 
 #endif  // MOJO_CC_OUTPUT_SURFACE_MOJO_H_