Added CHECKs for null pointers in ChromeAppSorting.

chrome/browser/extensions/chrome_app_sorting.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_CHROME_APP_SORTING_H_
 #define CHROME_BROWSER_EXTENSIONS_CHROME_APP_SORTING_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 11 matching lines @@
 
 class ExtensionScopedPrefs;
 
 class ChromeAppSorting : public AppSorting {
  public:
   ChromeAppSorting();
   ~ChromeAppSorting() override;
 
   // AppSorting implementation:
   void SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) override;
+  void CheckExtensionScopedPrefs() const override;
   void SetExtensionSyncService(
       ExtensionSyncService* extension_sync_service) override;
   void Initialize(const extensions::ExtensionIdList& extension_ids) override;
   void FixNTPOrdinalCollisions() override;
   void EnsureValidOrdinals(
       const std::string& extension_id,
       const syncer::StringOrdinal& suggested_page) override;
   void OnExtensionMoved(const std::string& moved_extension_id,
                         const std::string& predecessor_extension_id,
                         const std::string& successor_extension_id) override;
@@ skipping 133 matching lines @@
 
   // The set of extensions that don't appear in the new tab page.
   std::set<std::string> ntp_hidden_extensions_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeAppSorting);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_CHROME_APP_SORTING_H_