compositor-worker: Allow registering compositor-frame callbacks.

Source/modules/compositorworker/CompositorWorkerGlobalScope.idl

Index: Source/modules/compositorworker/CompositorWorkerGlobalScope.idl
diff --git a/Source/modules/compositorworker/CompositorWorkerGlobalScope.idl b/Source/modules/compositorworker/CompositorWorkerGlobalScope.idl
index bcb8410c0fba9f9e49e67f1f1a9e3b4c4f7d3fb4..fb9ec840463752fd3d3a9c4b6b2a926fc6041bc0 100644
--- a/Source/modules/compositorworker/CompositorWorkerGlobalScope.idl
+++ b/Source/modules/compositorworker/CompositorWorkerGlobalScope.idl
@@ -10,4 +10,7 @@
 ] interface CompositorWorkerGlobalScope : WorkerGlobalScope {
     [Custom, RaisesException] void postMessage(any message, optional sequence<Transferable> transfer);
     attribute EventHandler onmessage;
+
+    long requestAnimationFrame(FrameRequestCallback callback);
+    void cancelAnimationFrame(long handle);
 };