add support for forcing compositing mode

chrome/browser/tab_contents/render_view_host_delegate_helper.cc

 // Copyright (c) 2011 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 "chrome/browser/tab_contents/render_view_host_delegate_helper.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/string_util.h"
@@ skipping 275 matching lines @@
         command_line.HasSwitch(switches::kAllowFileAccessFromFiles);
     web_prefs.show_composited_layer_borders =
         command_line.HasSwitch(switches::kShowCompositedLayerBorders);
     web_prefs.show_composited_layer_tree =
         command_line.HasSwitch(switches::kShowCompositedLayerTree);
     web_prefs.show_fps_counter =
         command_line.HasSwitch(switches::kShowFPSCounter);
     web_prefs.accelerated_compositing_enabled =
         gpu_enabled() &&
         !command_line.HasSwitch(switches::kDisableAcceleratedCompositing);
+    web_prefs.force_compositing_mode =
+        command_line.HasSwitch(switches::kForceCompositingMode);
     web_prefs.accelerated_2d_canvas_enabled =
         gpu_enabled() &&
         command_line.HasSwitch(switches::kEnableAccelerated2dCanvas);
     web_prefs.accelerated_layers_enabled =
         !command_line.HasSwitch(switches::kDisableAcceleratedLayers);
     web_prefs.composite_to_texture_enabled =
         command_line.HasSwitch(switches::kEnableCompositeToTexture);
     web_prefs.accelerated_plugins_enabled =
         command_line.HasSwitch(switches::kEnableAcceleratedPlugins);
     web_prefs.accelerated_video_enabled =
@@ skipping 60 matching lines @@
   inspector_settings->SetWithoutPathExpansion(key,
                                               Value::CreateStringValue(value));
 }
 
 void RenderViewHostDelegateHelper::ClearInspectorSettings(Profile* profile) {
   DictionaryValue* inspector_settings =
       profile->GetPrefs()->GetMutableDictionary(
           prefs::kWebKitInspectorSettings);
   inspector_settings->Clear();
 }