Make Graphics3D::SwapBuffers take a completion callback

ppapi/cpp/dev/surface_3d_dev.h

 // Copyright (c) 2010 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 PPAPI_CPP_DEV_SURFACE_3D_DEV_H_
 #define PPAPI_CPP_DEV_SURFACE_3D_DEV_H_
 
 #include "ppapi/c/dev/ppb_surface_3d_dev.h"
 
+#include "ppapi/cpp/completion_callback.h"
 #include "ppapi/cpp/instance.h"
 #include "ppapi/cpp/resource.h"
 
 namespace pp {
 
 class CompletionCallback;
 
 class Surface3D_Dev : public Resource {
  public:
   // Creates an is_null() Surface3D object.
   Surface3D_Dev() {}
 
   Surface3D_Dev(const Instance& instance,
                 PP_Config3D_Dev config,
                 const int32_t* attrib_list);
 
-  // TODO(alokp): Add completion callback.
-  int32_t SwapBuffers() const;
+  int32_t SwapBuffers(const CompletionCallback& cc) const;
 
  protected:
   explicit Surface3D_Dev(PP_Resource resource_id) : Resource(resource_id) {}
   static Surface3D_Dev FromResource(PP_Resource resource_id);
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEV_SURFACE_3D_DEV_H_