Bug 1415182. Make the External interface [NoInterfaceObject], per spec. r=qdot

MozReview-Commit-ID: DCX4uxAFPAu

dom/tests/mochitest/general/test_interfaces.js

@@ -342,8 +342,6 @@ var interfaceNamesInGlobalScope =
     "EventSource",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "EventTarget",
-// IMPORTANT: Do not change this list without review from a DOM peer!
-    "External",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "File",
 // IMPORTANT: Do not change this list without review from a DOM peer!

dom/webidl/External.webidl

@@ -4,7 +4,7 @@
  * You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-[JSImplementation="@mozilla.org/sidebar;1"]
+[NoInterfaceObject, JSImplementation="@mozilla.org/sidebar;1"]
 interface External
 {
   [UnsafeInPrerendering] void AddSearchProvider(DOMString aDescriptionURL);