Fix bug with invalid chrome.sessions.onChanged listener.

chrome/browser/extensions/api/sessions/sessions_api.h

 // Copyright 2013 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_EXTENSIONS_API_SESSIONS_SESSIONS_API_H__
 #define CHROME_BROWSER_EXTENSIONS_API_SESSIONS_SESSIONS_API_H__
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 67 matching lines @@
   void SetResultRestoredTab(content::WebContents* contents);
   bool SetResultRestoredWindow(int window_id);
   bool RestoreMostRecentlyClosed(Browser* browser);
   bool RestoreLocalSession(const SessionId& session_id, Browser* browser);
   bool RestoreForeignSession(const SessionId& session_id,
                              Browser* browser);
 };
 
 class SessionsEventRouter : public sessions::TabRestoreServiceObserver {
  public:
-  explicit SessionsEventRouter(Profile* profile);
+  explicit SessionsEventRouter(Profile* profile,
+                               EventRouter::Observer* observer);
   ~SessionsEventRouter() override;
 
   // Observer callback for TabRestoreServiceObserver. Sends data on
   // recently closed tabs to the javascript side of this page to
   // display to the user.
   void TabRestoreServiceChanged(sessions::TabRestoreService* service) override;
 
   // Observer callback to notice when our associated TabRestoreService
   // is destroyed.
   void TabRestoreServiceDestroyed(
       sessions::TabRestoreService* service) override;
 
  private:
   Profile* profile_;
+  EventRouter::Observer* observer_;
 
   // TabRestoreService that we are observing.
   sessions::TabRestoreService* tab_restore_service_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionsEventRouter);
 };
 
 class SessionsAPI : public BrowserContextKeyedAPI,
                     public extensions::EventRouter::Observer {
  public:
@@ skipping 22 matching lines @@
 
   // Created lazily upon OnListenerAdded.
   scoped_ptr<SessionsEventRouter> sessions_event_router_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionsAPI);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SESSIONS_SESSIONS_API_H__