Add onChange event to preference extension APIs.

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 32a6356ca0367a8f9ce5ca56abad8be2933e14ca..58a5de23c75eff9032f76b342b90600a8056cd2e 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -37,6 +37,7 @@
 #include "content/common/property_bag.h"
 
 class ExtensionBrowserEventRouter;
+class ExtensionPreferenceEventRouter;
 class ExtensionServiceBackend;
 class ExtensionToolbarModel;
 class ExtensionUpdater;
@@ -561,6 +562,8 @@ class ExtensionService
 
   scoped_ptr<ExtensionBrowserEventRouter> browser_event_router_;
 
+  scoped_ptr<ExtensionPreferenceEventRouter> preference_event_router_;
+
   // A collection of external extension providers.  Each provider reads
   // a source of external extension information.  Examples include the
   // windows registry and external_extensions.json.