[PPAPI] Add browser tests for compositor API

ppapi/thunk/ppb_compositor_api.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 PPAPI_THUNK_PPB_COMPOSITOR_API_H_
 #define PPAPI_THUNK_PPB_COMPOSITOR_API_H_
 
 #include "base/memory/ref_counted.h"
 #include "ppapi/c/ppb_compositor.h"
 #include "ppapi/shared_impl/tracked_callback.h"
 
 namespace ppapi {
 namespace thunk {
 
 class PPAPI_THUNK_EXPORT PPB_Compositor_API {
  public:
   virtual ~PPB_Compositor_API() {}
   virtual PP_Resource AddLayer() = 0;
   virtual int32_t CommitLayers(
       const scoped_refptr<ppapi::TrackedCallback>& callback) = 0;
   virtual int32_t ResetLayers() = 0;
+
+  // Private API.
+  virtual void BindToInstance(bool bound) = 0;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_PPB_COMPOSITOR_API_H_