Remove references to WindowProxy as an interface.

src/components/script/dom/webidls/WindowProxy.webidl

@@ -1,9 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* FIXME WindowProxy doesn't actually have an interface according to the spec,
-         but I'm not sure how to do fallible unwrapping without this, since
-         we lack Gecko's XPCOM querying facilities. */
-interface WindowProxy {
-};