Move ownership of AppSorting from ExtensionPrefs to ExtensionSystem

extensions/shell/browser/shell_extension_system.h

Index: extensions/shell/browser/shell_extension_system.h
diff --git a/extensions/shell/browser/shell_extension_system.h b/extensions/shell/browser/shell_extension_system.h
index 3fd5d1148fda89fe451e074593e2e6a91e0a1899..4ac61d6e893589910496295610d16b4cd58cfe53 100644
--- a/extensions/shell/browser/shell_extension_system.h
+++ b/extensions/shell/browser/shell_extension_system.h
@@ -59,6 +59,7 @@ class ShellExtensionSystem : public ExtensionSystem {
   StateStore* rules_store() override;
   InfoMap* info_map() override;
   QuotaService* quota_service() override;
+  AppSorting* app_sorting() override;
   void RegisterExtensionWithRequestContexts(
       const Extension* extension,
       const base::Closure& callback) override;
@@ -80,6 +81,7 @@ class ShellExtensionSystem : public ExtensionSystem {
 
   scoped_ptr<RuntimeData> runtime_data_;
   scoped_ptr<QuotaService> quota_service_;
+  scoped_ptr<AppSorting> app_sorting_;
 
   // Signaled when the extension system has completed its startup tasks.
   OneShotEvent ready_;