Made OSMesa work on Mac for WebGL....

chrome/test/test_launcher_utils.cc

 // Copyright (c) 2010 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 "app/app_switches.h"
 #include "app/gfx/gl/gl_implementation.h"
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/path_service.h"
 #include "base/scoped_ptr.h"
@@ skipping 15 matching lines @@
   command_line->AppendSwitch(switches::kNoFirstRun);
 
   // No default browser check, it would create an info-bar (if we are not the
   // default browser) that could conflicts with some tests expectations.
   command_line->AppendSwitch(switches::kNoDefaultBrowserCheck);
 
   // Enable warning level logging so that we can see when bad stuff happens.
   command_line->AppendSwitch(switches::kEnableLogging);
   command_line->AppendSwitchASCII(switches::kLoggingLevel, "1");  // warning
 
-  // TODO(apatrick): Other pending changes will fix this for mac.
-#if !defined(OS_MACOSX)
   // Force all tests to use OSMesa if they launch the GPU process.
   command_line->AppendSwitchASCII(switches::kUseGL,
                                   gfx::kGLImplementationOSMesaName);
-#endif
+
+  // Mac does not support accelerated compositing with OSMesa.
+  // http://crbug.com/58343
+  command_line->AppendSwitch(switches::kDisableAcceleratedCompositing);
 }
 
 bool OverrideUserDataDir(const FilePath& user_data_dir) {
   bool success = true;
 
   // PathService::Override() is the best way to change the user data directory.
   // This matches what is done in ChromeMain().
   success = PathService::Override(chrome::DIR_USER_DATA, user_data_dir);
 
 #if defined(OS_LINUX)
   // Make sure the cache directory is inside our clear profile. Otherwise
   // the cache may contain data from earlier tests that could break the
   // current test.
   //
   // Note: we use an environment variable here, because we have to pass the
   // value to the child process. This is the simplest way to do it.
   scoped_ptr<base::Environment> env(base::Environment::Create());
   success = success && env->SetVar("XDG_CACHE_HOME", user_data_dir.value());
 #endif
 
   return success;
 }
 
 }  // namespace test_launcher_utils