Make GL calls go through subclassable class.

ui/gl/gl_glx_api_implementation.cc

+// Copyright (c) 2012 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 "ui/gl/gl_glx_api_implementation.h"
+
+namespace gfx {
+
+RealGLXApi g_real_glx;
+
+void InitializeGLBindingsGLX() {
+  g_driver_glx.InitializeBindings();
+  g_real_glx.Initialize(&g_driver_glx);
+  g_current_glx_context = &g_real_glx;
+}
+
+void InitializeGLExtensionBindingsGLX(GLContext* context) {
+  g_driver_glx.InitializeExtensionBindings(context);
+}
+
+void InitializeDebugGLBindingsGLX() {
+  g_driver_glx.InitializeDebugBindings();
+}
+
+void ClearGLBindingsGLX() {
+  g_driver_glx.ClearBindings();
+}
+
+GLXApi::GLXApi() {
+}
+
+GLXApi::~GLXApi() {
+}
+
+RealGLXApi::RealGLXApi() {
+}
+
+void RealGLXApi::Initialize(DriverGLX* driver) {
+  driver_ = driver;
+}
+
+}  // namespace gfx
+
+