Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/modules/vr/VRFieldOfView.idl

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // http://mozvr.github.io/webvr-spec/webvr.html#vrfieldofview
 [
     RuntimeEnabled=WebVR,
-    GarbageCollected,
     Constructor(optional VRFieldOfViewInit fov),
 ] interface VRFieldOfView {
     attribute double upDegrees;
     attribute double downDegrees;
     attribute double leftDegrees;
     attribute double rightDegrees;
 };