Move modules-related attributes out from Window.idl.

Source/modules/mediastream/WindowMediaStream.idl

Index: Source/modules/mediastream/WindowMediaStream.idl
diff --git a/Source/modules/mediastream/WindowMediaStream.idl b/Source/modules/mediastream/WindowMediaStream.idl
new file mode 100644
index 0000000000000000000000000000000000000000..f5b14fcdd4375c46104b19a30ff5c184580394de
--- /dev/null
+++ b/Source/modules/mediastream/WindowMediaStream.idl
@@ -0,0 +1,11 @@
+// Copyright (c) 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.
+
+[
+    ImplementedAs=DOMWindowMediaStream,
+] partial interface Window {
+    [RuntimeEnabled=MediaStream] attribute MediaStreamConstructor webkitMediaStream;
+
+    [RuntimeEnabled=PeerConnection] attribute RTCPeerConnectionConstructor webkitRTCPeerConnection;
+};