Fix crashes in ExtensionService

chrome/browser/sessions/session_restore.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/session_restore.h"
 
 #include <algorithm>
 #include <list>
 #include <set>
 #include <vector>
@@ skipping 625 matching lines @@
                   bool schedule_load) {
     DCHECK(!tab.navigations.empty());
     int selected_index = tab.current_navigation_index;
     selected_index = std::max(
         0,
         std::min(selected_index,
                  static_cast<int>(tab.navigations.size() - 1)));
 
     // Record an app launch, if applicable.
     GURL url = tab.navigations.at(tab.current_navigation_index).virtual_url();
-    if (browser->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 = browser->profile()->GetExtensionService();
+    if (service && service->IsInstalledApp(url)) {
       UMA_HISTOGRAM_ENUMERATION(extension_misc::kAppLaunchHistogram,
                                 extension_misc::APP_LAUNCH_SESSION_RESTORE,
                                 extension_misc::APP_LAUNCH_BUCKET_BOUNDARY);
     }
 
     TabContents* tab_contents =
         browser->AddRestoredTab(tab.navigations,
                                 tab_index,
                                 selected_index,
                                 tab.extension_app_id,
@@ skipping 168 matching lines @@
 void SessionRestore::RestoreSessionSynchronously(
     Profile* profile,
     const std::vector<GURL>& urls_to_open) {
   Restore(profile, NULL, true, false, true, urls_to_open);
 }
 
 // static
 bool SessionRestore::IsRestoring() {
   return restoring;
 }