Added CHECKs for null pointers in ChromeAppSorting.

extensions/browser/app_sorting.h

 // Copyright (c) 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 EXTENSIONS_BROWSER_APP_SORTING_H_
 #define EXTENSIONS_BROWSER_APP_SORTING_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "extensions/common/extension.h"
 #include "sync/api/string_ordinal.h"
 
 class ExtensionSyncService;
 
 namespace extensions {
 
 class ExtensionScopedPrefs;
 
 // An interface that provides a fixed ordering for a set of apps.
 class AppSorting {
  public:
   AppSorting() {}
   virtual ~AppSorting() {}
 
   // Sets the object used to look up preferences. Ownership remains with the
   // caller.
   virtual void SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) = 0;
 
+  // CHECKs that SetExtensionScopedPrefs has been called with a non-null object.
+  // TODO(mgiuca): Added this to try and diagnose http://crbug.com/476648.
+  // Remove it after the investigation is concluded.
+  virtual void CheckExtensionScopedPrefs() const = 0;
+
   // Sets up the ExtensionSyncService to inform of changes that require syncing.
   virtual void SetExtensionSyncService(
       ExtensionSyncService* extension_sync_service) = 0;
 
   // Properly initializes internal values that require |extension_ids|.
+  // SetExtensionScopedPrefs must have been called prior to this.
   virtual void Initialize(const extensions::ExtensionIdList& extension_ids) = 0;
 
   // Resolves any conflicts the might be created as a result of syncing that
   // results in two icons having the same page and app launch ordinal. After
   // this is called it is guaranteed that there are no collisions of NTP icons.
   virtual void FixNTPOrdinalCollisions() = 0;
 
   // This ensures that the extension has valid ordinals, and if it doesn't then
   // properly initialize them. |suggested_page| will be used if it is valid and
   // the extension has no valid user-set page ordinal.
@@ skipping 69 matching lines @@
   virtual void SetExtensionVisible(const std::string& extension_id,
                                    bool visible) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AppSorting);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_APP_SORTING_H_