Observe adding external extensions via windows registry.

chrome/browser/extensions/external_loader.cc

Index: chrome/browser/extensions/external_loader.cc
diff --git a/chrome/browser/extensions/external_loader.cc b/chrome/browser/extensions/external_loader.cc
index c706a436bfdfb4681961029c99713eff3d943963..662cdebbd16acdbb7943261e043b127b0443965a 100644
--- a/chrome/browser/extensions/external_loader.cc
+++ b/chrome/browser/extensions/external_loader.cc
@@ -44,4 +44,11 @@ void ExternalLoader::LoadFinished() {
   }
 }
 
+void ExternalLoader::OnUpdated(
+    scoped_ptr<base::DictionaryValue> updated_prefs) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (owner_)
+    owner_->UpdatePrefs(updated_prefs.release());
+}
+
 }  // namespace extensions