[Mojo] Fix race condition in sample_app's SwapBuffers

mojo/public/bindings/gles2_client/gles2_client_impl.h

 // Copyright 2013 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_PUBLIC_BINDINGS_GLES2_CLIENT_GLES2_CLIENT_IMPL_H_
 #define MOJO_PUBLIC_BINDINGS_GLES2_CLIENT_GLES2_CLIENT_IMPL_H_
 
 #include "mojo/public/bindings/lib/remote_ptr.h"
 #include "mojom/gles2.h"
 
 namespace mojo {
+class GLES2ClientImpl;
 
 class GLES2Delegate {
  public:
   virtual ~GLES2Delegate();
-  virtual void DidCreateContext(GLES2* gl, uint32_t width, uint32_t height);
-  virtual void ContextLost(GLES2* gl);
+  virtual void DidCreateContext(
+      GLES2ClientImpl* gl, uint32_t width, uint32_t height);
+  virtual void ContextLost(GLES2ClientImpl* gl);
 };
 
 class GLES2ClientImpl : public GLES2ClientStub {
  public:
   explicit GLES2ClientImpl(GLES2Delegate* delegate,
                            ScopedMessagePipeHandle gl);
   virtual ~GLES2ClientImpl();
 
   static void Initialize();
   static void Terminate();
 
-  GLES2* gl() {
-    return gl_.get();
-  }
+  void SwapBuffers();
 
  private:
   virtual void DidCreateContext(
     uint64_t encoded, uint32_t width, uint32_t height) MOJO_OVERRIDE;
   virtual void ContextLost() MOJO_OVERRIDE;
 
   GLES2Delegate* delegate_;
   RemotePtr<GLES2> gl_;
 };
 
 }  // mojo
 
 #endif  // MOJO_PUBLIC_BINDINGS_GLES2_CLIENT_GLES2_CLIENT_IMPL_H_