Split surface id and simplify connecting to surfaces service

sky/compositor/surface_allocator.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 SKY_COMPOSITOR_SURFACE_ALLOCATOR_H_
 #define SKY_COMPOSITOR_SURFACE_ALLOCATOR_H_
 
 #include "base/basictypes.h"
+#include "mojo/services/surfaces/public/interfaces/surface_id.mojom.h"
 
 namespace sky {
 
 class SurfaceAllocator {
  public:
   SurfaceAllocator(uint32_t id_namespace);
   ~SurfaceAllocator();
 
-  uint64_t CreateSurfaceId();
+  mojo::SurfaceIdPtr CreateSurfaceId();
 
  private:
   uint32_t id_namespace_;
   uint32_t next_id_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceAllocator);
 };
 
 }  // namespace sky
 
 #endif  // SKY_COMPOSITOR_SURFACE_ALLOCATOR_H_