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

third_party/WebKit/Source/core/dom/DOMMatrixReadOnly.idl

 // Copyright 2014 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://dev.w3.org/fxtf/geometry/#DOMMatrix
 
 [
     // FIXME: Constructor(sequence<unrestricted double> numberSequence)
     // FIXME: Exposed=(Window,Worker)
-    GarbageCollected,
     RuntimeEnabled=GeometryInterfaces,
 ] interface DOMMatrixReadOnly {
     // These attributes are simple aliases for certain elements of the 4x4 matrix
     readonly attribute unrestricted double a;
     readonly attribute unrestricted double b;
     readonly attribute unrestricted double c;
     readonly attribute unrestricted double d;
     readonly attribute unrestricted double e;
     readonly attribute unrestricted double f;
 
@@ skipping 33 matching lines @@
                               optional unrestricted double scaleY = 1,
                               optional unrestricted double scaleZn = 1,
                               optional unrestricted double originX = 0,
                               optional unrestricted double originY = 0,
                               optional unrestricted double originZ = 0);
     DOMMatrix multiply(DOMMatrix other);
 
     Float32Array toFloat32Array();
     Float64Array toFloat64Array();
 };