Cache the current WebPreferences on RenderViewHostImpl.

content/public/browser/render_view_host.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_RENDER_VIEW_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_VIEW_HOST_H_
 
 #include <list>
 
 #include "base/callback_forward.h"
@@ skipping 176 matching lines @@
   virtual void SetWebUIProperty(const std::string& name,
                                 const std::string& value) = 0;
 
   // Changes the zoom level for the current main frame.
   virtual void Zoom(PageZoom zoom) = 0;
 
   // Send the renderer process the current preferences supplied by the
   // RenderViewHostDelegate.
   virtual void SyncRendererPrefs() = 0;
 
   // Returns the current WebKit preferences.

[jam, 2014/07/21 17:40:33]

nit: now that the behavior of this method changed to return a cached version,
this should be called out in the comment

[chrishtr, 2014/07/21 18:16:07]

Done.

   virtual WebPreferences GetWebkitPreferences() = 0;
 
+  // If any state that affects the webkit preferences changed, this method must
+  // be called. This triggers recomputing preferences.
+  virtual void OnWebkitPreferencesChanged() = 0;
+
   // Passes a list of Webkit preferences to the renderer.
   virtual void UpdateWebkitPreferences(const WebPreferences& prefs) = 0;
 
   // Retrieves the list of AudioOutputController objects associated
   // with this object and passes it to the callback you specify, on
   // the same thread on which you called the method.
   typedef std::list<scoped_refptr<media::AudioOutputController> >
       AudioOutputControllerList;
   typedef base::Callback<void(const AudioOutputControllerList&)>
       GetAudioOutputControllersCallback;
@@ skipping 14 matching lines @@
 
  private:
   // This interface should only be implemented inside content.
   friend class RenderViewHostImpl;
   RenderViewHost() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_VIEW_HOST_H_