Enable sync for the settings from the Extension Settings API.

chrome/browser/extensions/extension_service.h

Index: chrome/browser/extensions/extension_service.h
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 276406cd500848793bfe8191d068724cb129ee31..67a66827eb7717af5844a94285710124ad6c76ad 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -77,6 +77,8 @@ class ExtensionServiceInterface : public SyncableService {
 
   virtual ~ExtensionServiceInterface() {}
   virtual const ExtensionList* extensions() const = 0;
+  virtual const ExtensionList* disabled_extensions() const = 0;
+  virtual const ExtensionList* terminated_extensions() const = 0;
   virtual PendingExtensionManager* pending_extension_manager() = 0;
 
   // Install an update.  Return true if the install can be started.
@@ -186,8 +188,8 @@ class ExtensionService
 
   // Gets the list of currently installed extensions.
   virtual const ExtensionList* extensions() const OVERRIDE;
-  const ExtensionList* disabled_extensions() const;
-  const ExtensionList* terminated_extensions() const;
+  virtual const ExtensionList* disabled_extensions() const OVERRIDE;
+  virtual const ExtensionList* terminated_extensions() const OVERRIDE;
 
   // Gets the object managing the set of pending extensions.
   virtual PendingExtensionManager* pending_extension_manager() OVERRIDE;