Add MGL entry points and port spinning_cube to use them

examples/spinning_cube/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 EXAMPLES_SPINNING_CUBE_GLES2_CLIENT_IMPL_H_
 #define EXAMPLES_SPINNING_CUBE_GLES2_CLIENT_IMPL_H_
 
 #include "examples/spinning_cube/spinning_cube.h"
-#include "mojo/public/c/gles2/gles2.h"
+#include "mojo/public/c/gpu/MGL/mgl.h"
 #include "mojo/services/geometry/public/interfaces/geometry.mojom.h"
 #include "mojo/services/native_viewport/public/interfaces/native_viewport.mojom.h"
 
 namespace examples {
 
 class GLES2ClientImpl {
  public:
   explicit GLES2ClientImpl(mojo::ContextProviderPtr context_provider);
   virtual ~GLES2ClientImpl();
 
   void SetSize(const mojo::Size& size);
   void HandleInputEvent(const mojo::Event& event);
   void Draw();
 
  private:
   void ContextCreated(mojo::CommandBufferPtr command_buffer);
   void ContextLost();
   static void ContextLostThunk(void* closure);
   void WantToDraw();
 
   MojoTimeTicks last_time_;
   mojo::Size size_;
   SpinningCube cube_;
   mojo::PointF capture_point_;
   mojo::PointF last_drag_point_;
   MojoTimeTicks drag_start_time_;
   bool waiting_to_draw_;
 
   mojo::ContextProviderPtr context_provider_;
-  MojoGLES2Context context_;
+  MGLContext context_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(GLES2ClientImpl);
 };
 
 }  // namespace examples
 
 #endif  // EXAMPLES_SPINNING_CUBE_GLES2_CLIENT_IMPL_H_