Added CHECKs for null pointers in ChromeAppSorting.

extensions/browser/extension_prefs.cc

 // Copyright 2014 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 "extensions/browser/extension_prefs.h"
 
 #include <iterator>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 1849 matching lines @@
     scoped_ptr<TimeProvider> time_provider,
     bool extensions_disabled,
     const std::vector<ExtensionPrefsObserver*>& early_observers)
     : prefs_(prefs),
       install_directory_(root_dir),
       extension_pref_value_map_(extension_pref_value_map),
       app_sorting_(app_sorting.Pass()),
       time_provider_(time_provider.Pass()),
       extensions_disabled_(extensions_disabled) {
   app_sorting_->SetExtensionScopedPrefs(this);
+  // TODO(mgiuca): Added this CHECK to try and diagnose http://crbug.com/476648.
+  // Remove it after the investigation is concluded.
+  app_sorting_->CheckExtensionScopedPrefs();
   MakePathsRelative();
 
   // Ensure that any early observers are watching before prefs are initialized.
   for (std::vector<ExtensionPrefsObserver*>::const_iterator iter =
            early_observers.begin();
        iter != early_observers.end();
        ++iter) {
     AddObserver(*iter);
   }
 
@@ skipping 261 matching lines @@
   extension_pref_value_map_->RegisterExtension(
       extension_id, install_time, is_enabled, is_incognito_enabled);
 
   FOR_EACH_OBSERVER(
       ExtensionPrefsObserver,
       observer_list_,
       OnExtensionRegistered(extension_id, install_time, is_enabled));
 }
 
 }  // namespace extensions