Move ownership of AppSorting from ExtensionPrefs to ExtensionSystem

extensions/browser/extension_system.h

Index: extensions/browser/extension_system.h
diff --git a/extensions/browser/extension_system.h b/extensions/browser/extension_system.h
index fcc0164d35892dc646f63280563f7e4c65b1fccd..b431dde319789a23d9b42d2fe2fb1dd1b4ce0130 100644
--- a/extensions/browser/extension_system.h
+++ b/extensions/browser/extension_system.h
@@ -30,6 +30,7 @@ class BrowserContext;
 
 namespace extensions {
 
+class AppSorting;
 class ContentVerifier;
 class Extension;
 class ExtensionSet;
@@ -86,6 +87,9 @@ class ExtensionSystem : public KeyedService {
   // Lives on the UI thread. Created at startup.
   virtual QuotaService* quota_service() = 0;
 
+  // Returns the AppSorting which provides an ordering for all installed apps.
+  virtual AppSorting* app_sorting() = 0;
+
   // Called by the ExtensionService that lives in this system. Gives the
   // info map a chance to react to the load event before the EXTENSION_LOADED
   // notification has fired. The purpose for handling this event first is to