Use C OpenGL interface in mojo::GLContext

mojo/public/platform/native/gles2_impl_chromium_sub_image_thunks.cc

-// Copyright 2015 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.
-
-#include "mojo/public/platform/native/gles2_impl_chromium_sub_image_thunks.h"
-
-#include <assert.h>
-
-#include "mojo/public/platform/native/thunk_export.h"
-
-extern "C" {
-static MojoGLES2ImplChromiumSubImageThunks g_impl_chromium_sub_image_thunks = {
-    0};
-
-#define VISIT_GL_CALL(Function, ReturnType, PARAMETERS, ARGUMENTS) \
-  ReturnType GL_APIENTRY gl##Function PARAMETERS {                 \
-    assert(g_impl_chromium_sub_image_thunks.Function);             \
-    return g_impl_chromium_sub_image_thunks.Function ARGUMENTS;    \
-  }
-#include "mojo/public/c/gles2/gles2_call_visitor_chromium_sub_image_autogen.h"
-#undef VISIT_GL_CALL
-
-extern "C" THUNK_EXPORT size_t MojoSetGLES2ImplChromiumSubImageThunks(
-    const MojoGLES2ImplChromiumSubImageThunks*
-        gles2_impl_chromium_sub_image_thunks) {
-  if (gles2_impl_chromium_sub_image_thunks->size >=
-      sizeof(g_impl_chromium_sub_image_thunks))
-    g_impl_chromium_sub_image_thunks = *gles2_impl_chromium_sub_image_thunks;
-  return sizeof(g_impl_chromium_sub_image_thunks);
-}
-
-}  // extern "C"