Cache the current WebPreferences on RenderViewHostImpl.

chrome/browser/android/voice_search_tab_helper.cc

 // Copyright 2014 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/android/voice_search_tab_helper.h"
 
 #include "components/google/core/browser/google_util.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/web_preferences.h"
@@ skipping 14 matching lines @@
   content::WebPreferences prefs = host->GetWebkitPreferences();
 
   // In the case where media autoplay has been enabled by default (e.g. in
   // performance media tests) do not update it based on navigation changes.
   //
   // Note that GetWekitPreferences() is 'stateless'. It returns the default
   // webkit preferences configuration from command line switches.
   if (!prefs.user_gesture_required_for_media_playback)
     return;
 
+  // TODO(chrishtr): this is wrong. user_gesture_required_for_media_playback
+  // will be reset the next time a preference changes.
   prefs.user_gesture_required_for_media_playback =
       !google_util::IsGoogleSearchUrl(web_contents->GetLastCommittedURL());
   host->UpdateWebkitPreferences(prefs);
 }