cc: Plumb group id through animation creation and start/finish notifications

cc/blink/web_compositor_support_impl.cc

Index: cc/blink/web_compositor_support_impl.cc
diff --git a/cc/blink/web_compositor_support_impl.cc b/cc/blink/web_compositor_support_impl.cc
index 807384643dd412cb6d8abc7d8ca7fcf68989faf1..ae098fc867e462745793964258dc2c162e9fc5af 100644
--- a/cc/blink/web_compositor_support_impl.cc
+++ b/cc/blink/web_compositor_support_impl.cc
@@ -94,8 +94,15 @@ WebScrollbarLayer* WebCompositorSupportImpl::createSolidColorScrollbarLayer(
 WebCompositorAnimation* WebCompositorSupportImpl::createAnimation(
     const blink::WebCompositorAnimationCurve& curve,
     blink::WebCompositorAnimation::TargetProperty target,
+#ifdef WEB_COMPOSITOR_SUPPORT_CREATE_ANIMATION_SUPPORTS_GROUP
+    int group_id,
+#endif
     int animation_id) {
+#ifdef WEB_COMPOSITOR_SUPPORT_CREATE_ANIMATION_SUPPORTS_GROUP
+  return new WebCompositorAnimationImpl(curve, target, animation_id, group_id);
+#else
   return new WebCompositorAnimationImpl(curve, target, animation_id, 0);
+#endif
 }
 
 WebFilterAnimationCurve*