Only send events to renderers that are listening to an event....

chrome/browser/renderer_host/browser_render_process_host.h

 // Copyright (c) 2006-2008 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 CHROME_BROWSER_RENDERER_HOST_BROWSER_RENDER_PROCESS_HOST_H_
 #define CHROME_BROWSER_RENDERER_HOST_BROWSER_RENDER_PROCESS_HOST_H_
 
 #include "build/build_config.h"
 
 #include <string>
@@ skipping 68 matching lines @@
   // corrupted and thus needs to be terminated using this call. This function
   // can be safely called from any thread.
   static void BadMessageTerminateProcess(uint16 msg_type,
                                          base::ProcessHandle renderer);
 
   // NotificationObserver implementation.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
 
+  // An extension process started or stopped listening to an event.
+  void OnExtensionAddListener(const std::string& event_name);
+  void OnExtensionRemoveListener(const std::string& event_name);
+
  private:
   // Control message handlers.
   void OnPageContents(const GURL& url, int32 page_id,
                       const std::wstring& contents);
   void OnUpdatedCacheStats(const WebKit::WebCache::UsageStats& stats);
   void SuddenTerminationChanged(bool enabled);
 
   // Initialize support for visited links. Send the renderer process its initial
   // set of visited links.
   void InitVisitedLinks();
@@ skipping 46 matching lines @@
   // This is used to clear our cache five seconds after the last use.
   base::DelayTimer<BrowserRenderProcessHost> cached_dibs_cleaner_;
 
   // Used in single-process mode.
   scoped_ptr<RendererMainThread> in_process_renderer_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserRenderProcessHost);
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_BROWSER_RENDER_PROCESS_HOST_H_