Use stub GL draw/clear calls for browser tests that do not need pixels.

ui/gl/gl_gl_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_gl_api_implementation.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 185 matching lines @@
 }
 
 void InitializeGLExtensionBindingsGL(GLContext* context) {
   g_driver_gl.InitializeExtensions(context);
 }
 
 void InitializeDebugGLBindingsGL() {
   g_driver_gl.InitializeDebugBindings();
 }
 
+void InitializeStubGLBindingsGL() { g_driver_gl.InitializeStubBindings(); }
+
 void ClearGLBindingsGL() {
   if (g_real_gl) {
     delete g_real_gl;
     g_real_gl = NULL;
   }
   if (g_trace_gl) {
     delete g_trace_gl;
     g_trace_gl = NULL;
   }
   g_gl = NULL;
@@ skipping 119 matching lines @@
 const GLubyte* VirtualGLApi::glGetStringFn(GLenum name) {
   switch (name) {
     case GL_EXTENSIONS:
       return reinterpret_cast<const GLubyte*>(extensions_.c_str());
     default:
       return driver_->fn.glGetStringFn(name);
   }
 }
 
 }  // namespace gfx