Fix crashes in ExtensionService

chrome/browser/sessions/tab_restore_service.cc

 // Copyright (c) 2010 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/sessions/tab_restore_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 
@@ skipping 137 matching lines @@
           return;
         }
       }
     }
   }
 }
 
 void RecordAppLaunch(Browser* browser, const TabRestoreService::Tab& tab) {
   GURL url = tab.navigations.at(tab.current_navigation_index).virtual_url();
   Profile* profile = browser->profile();
-  if (!profile->GetExtensionService()->IsInstalledApp(url))
+  // TODO: the ExtensionService should never be NULL, but in some cases it is,
+  // see bug 73768. After it is resolved, the explicit test can go away.
+  ExtensionService* service = profile->GetExtensionService();
+  if (!service || !service->IsInstalledApp(url))
     return;
 
   UMA_HISTOGRAM_ENUMERATION(extension_misc::kAppLaunchHistogram,
                             extension_misc::APP_LAUNCH_NTP_RECENTLY_CLOSED,
                             extension_misc::APP_LAUNCH_BUCKET_BOUNDARY);
 }
 
 }  // namespace
 
 TabRestoreService::Tab::Tab()
@@ skipping 906 matching lines @@
   // correctly write out the entries when Save is invoked (Save starts from
   // the front, not the end and we just added the entries to the end).
   entries_to_write_ = staging_entries_.size();
 
   PruneAndNotify();
 }
 
 Time TabRestoreService::TimeNow() const {
   return time_factory_ ? time_factory_->TimeNow() : Time::Now();
 }