Use C OpenGL interface in mojo::GLContext

mojo/gpu/gl_context.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_GPU_GL_CONTEXT_H_
 #define MOJO_GPU_GL_CONTEXT_H_
 
 #include "base/basictypes.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "mojo/public/c/gles2/gles2.h"
 
 namespace gpu {
 namespace gles2 {
 class GLES2Interface;
 }
 }
 
 namespace mojo {
+class MojoGLES2Impl;
 class Shell;
 
 class GLContext {
  public:
   class Observer {
    public:
     virtual void OnContextLost() = 0;
 
    protected:
     virtual ~Observer();
   };
 
   static base::WeakPtr<GLContext> Create(Shell* shell);
 
   void MakeCurrent();
   void Destroy();
 
-  gpu::gles2::GLES2Interface* gl() const { return gl_; }
+  gpu::gles2::GLES2Interface* gl() const;
 
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
  private:
   explicit GLContext(Shell* shell);
   ~GLContext();
 
   static void ContextLostThunk(void* self);
   void OnContextLost();
 
   MojoGLES2Context context_;
-  gpu::gles2::GLES2Interface* gl_;
+  scoped_ptr<MojoGLES2Impl> gl_impl_;
 
   base::ObserverList<Observer> observers_;
   base::WeakPtrFactory<GLContext> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GLContext);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_GPU_GL_CONTEXT_H_