Add CSS variables feature flag to chrome://flags.

content/browser/web_contents/web_contents_impl.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 "content/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 469 matching lines @@
   prefs.accelerated_plugins_enabled =
       !command_line.HasSwitch(switches::kDisableAcceleratedPlugins);
   prefs.accelerated_video_enabled =
       !command_line.HasSwitch(switches::kDisableAcceleratedVideo);
   prefs.fullscreen_enabled =
       !command_line.HasSwitch(switches::kDisableFullScreen);
   prefs.css_regions_enabled =
       command_line.HasSwitch(switches::kEnableCssRegions);
   prefs.css_shaders_enabled =
       command_line.HasSwitch(switches::kEnableCssShaders);
+  prefs.css_variables_enabled =
+      command_line.HasSwitch(switches::kEnableCssVariables);
   prefs.device_supports_touch =
       ui::GetDisplayLayout() == ui::LAYOUT_TOUCH;
 #if defined(OS_ANDROID)
   prefs.device_supports_mouse = false;
 #endif
 
 #if defined(OS_MACOSX)
   bool default_enable_scroll_animator = true;
 #else
   // On CrOS, the launcher always passes in the --enable flag.
@@ skipping 2617 matching lines @@
       browser_plugin_host()->embedder_render_process_host();
   *embedder_container_id = browser_plugin_host()->instance_id();
   int embedder_process_id =
       embedder_render_process_host ? embedder_render_process_host->GetID() : -1;
   if (embedder_process_id != -1) {
     *embedder_channel_name =
         StringPrintf("%d.r%d", render_view_host->GetProcess()->GetID(),
                      embedder_process_id);
   }
 }