compositor-worker: Introduce CompositorProxy.

Source/core/dom/CompositorProxy.idl

Index: Source/core/dom/CompositorProxy.idl
diff --git a/Source/core/dom/CompositorProxy.idl b/Source/core/dom/CompositorProxy.idl
new file mode 100644
index 0000000000000000000000000000000000000000..4b7be63c62eb2e31ca793941c40b91895174f6e0
--- /dev/null
+++ b/Source/core/dom/CompositorProxy.idl
@@ -0,0 +1,15 @@
+// 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.
+
+[
+    Constructor(Element element, DOMString[] attributeArray),
+    ConstructorCallWith=ExecutionContext,
+    Exposed=Window,
+    GarbageCollected,
+    RaisesException=Constructor,
+    RuntimeEnabled=CompositorWorker,
+] interface CompositorProxy {
+    readonly attribute long elementId;

[esprehn, 2015/03/25 23:21:48]

I don't think we should be exposing these ids to the page, they're an
implementation detail.

+    readonly attribute long attributes;

[esprehn, 2015/03/25 23:21:48]

This is just for hacking? We don't use bit fields like this in web apis.

[sadrul, 2015/03/27 17:23:29]

Both of these are for testing, yes. I have removed both, and updated the test to
use the 'supports()' API call instead.

+};