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

ui/gl/init/gl_initializer_x11.cc

 // Copyright 2016 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/init/gl_initializer.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 156 matching lines @@
   base::ThreadRestrictions::ScopedAllowIO allow_io;
 
   switch (implementation) {
     case kGLImplementationOSMesaGL:
       return InitializeStaticGLBindingsOSMesaGL();
     case kGLImplementationDesktopGL:
       return InitializeStaticGLXInternal();
     case kGLImplementationEGLGLES2:
       return InitializeStaticEGLInternal();
     case kGLImplementationMockGL:
-      SetGLImplementation(kGLImplementationMockGL);
+    case kGLImplementationStubGL:
+      SetGLImplementation(implementation);
       InitializeStaticGLBindingsGL();
       return true;
     default:
       NOTREACHED();
   }
 
   return false;
 }
 
 void InitializeDebugGLBindings() {
   InitializeDebugGLBindingsEGL();
   InitializeDebugGLBindingsGL();
   InitializeDebugGLBindingsGLX();
   InitializeDebugGLBindingsOSMESA();
 }
 
 void ShutdownGLPlatform() {
   GLSurfaceEGL::ShutdownOneOff();
   ClearBindingsEGL();
   ClearBindingsGL();
   ClearBindingsGLX();
   ClearBindingsOSMESA();
 }
 
 }  // namespace init
 }  // namespace gl