Add a command line switch to control accelerated 2d canvas

chrome/browser/tab_contents/render_view_host_delegate_helper.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 "chrome/browser/tab_contents/render_view_host_delegate_helper.h"
 
 #include "base/command_line.h"
 #include "base/string_util.h"
 #include "chrome/browser/background_contents_service.h"
 #include "chrome/browser/browser.h"
@@ skipping 250 matching lines @@
     web_prefs.experimental_webgl_enabled =
         command_line.HasSwitch(switches::kEnableExperimentalWebGL);
     web_prefs.site_specific_quirks_enabled =
         !command_line.HasSwitch(switches::kDisableSiteSpecificQuirks);
     web_prefs.allow_file_access_from_file_urls =
         command_line.HasSwitch(switches::kAllowFileAccessFromFiles);
     web_prefs.show_composited_layer_borders =
         command_line.HasSwitch(switches::kShowCompositedLayerBorders);
     web_prefs.accelerated_compositing_enabled =
         command_line.HasSwitch(switches::kEnableAcceleratedCompositing);
+    web_prefs.accelerated_2d_canvas_enabled =
+        command_line.HasSwitch(switches::kEnableAccelerated2dCanvas);
     web_prefs.memory_info_enabled =
         command_line.HasSwitch(switches::kEnableMemoryInfo);
     // The user stylesheet watcher may not exist in a testing profile.
     if (profile->GetUserStyleSheetWatcher()) {
       web_prefs.user_style_sheet_enabled = true;
       web_prefs.user_style_sheet_location =
           profile->GetUserStyleSheetWatcher()->user_style_sheet();
     } else {
       web_prefs.user_style_sheet_enabled = false;
     }
@@ skipping 14 matching lines @@
   }
   DCHECK(!web_prefs.default_encoding.empty());
 
   if (is_dom_ui) {
     web_prefs.loads_images_automatically = true;
     web_prefs.javascript_enabled = true;
   }
 
   return web_prefs;
 }