Refactor GL bindings so there is no global GLApi or DriverGL.

ui/gl/gl_wgl_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_wgl_api_implementation.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "ui/gl/gl_implementation.h"
 
 namespace gl {
 
-RealWGLApi* g_real_wgl;
+RealWGLApi* g_real_wgl = nullptr;
+DebugWGLApi* g_debug_wgl = nullptr;
 
 void InitializeStaticGLBindingsWGL() {
   g_driver_wgl.InitializeStaticBindings();
   if (!g_real_wgl) {
     g_real_wgl = new RealWGLApi();
   }
   g_real_wgl->Initialize(&g_driver_wgl);
   g_current_wgl_context = g_real_wgl;
   g_driver_wgl.InitializeExtensionBindings();
 }
 
 void InitializeDebugGLBindingsWGL() {
-  g_driver_wgl.InitializeDebugBindings();
+  if (!g_debug_wgl) {
+    g_debug_wgl = new DebugWGLApi(g_real_wgl);
+  }
+  g_current_wgl_context = g_debug_wgl;
 }
 
 void ClearBindingsWGL() {
+  if (g_debug_wgl) {
+    delete g_debug_wgl;
+    g_debug_wgl = NULL;
+  }
   if (g_real_wgl) {
     delete g_real_wgl;
     g_real_wgl = NULL;
   }
   g_current_wgl_context = NULL;
   g_driver_wgl.ClearBindings();
 }
 
 WGLApi::WGLApi() {
 }
@@ skipping 63 matching lines @@
     return NULL;
 
   const char* str = WGLApiBase::wglGetExtensionsStringEXTFn();
   if (!str)
     return NULL;
 
   filtered_ext_exts_ = FilterGLExtensionList(str, disabled_exts_);
   return filtered_ext_exts_.c_str();
 }
 
+DebugWGLApi::DebugWGLApi(WGLApi* wgl_api) : wgl_api_(wgl_api) {}
+
+DebugWGLApi::~DebugWGLApi() {}
+
 TraceWGLApi::~TraceWGLApi() {
 }
 
 bool GetGLWindowSystemBindingInfoWGL(GLWindowSystemBindingInfo* info) {
   const char* extensions = wglGetExtensionsStringEXT();
   *info = GLWindowSystemBindingInfo();
   if (extensions)
     info->extensions = extensions;
   return true;
 }
 
 }  // namespace gl