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 2cbdd5f1374b37313b5c0e79b65cd9177b8eed92..f6068936d082488ccee9f45435dabac07160499a 100644
--- a/extensions/shell/browser/shell_extension_system.h
+++ b/extensions/shell/browser/shell_extension_system.h
@@ -58,6 +58,7 @@ 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) override;
   void UnregisterExtensionWithRequestContexts(
@@ -76,6 +77,7 @@ 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_;