Make it possible to custom-paint without an Element.

sky/engine/core/painting/PaintingTasks.h

Index: sky/engine/core/painting/PaintingTasks.h
diff --git a/sky/engine/core/painting/PaintingTasks.h b/sky/engine/core/painting/PaintingTasks.h
index 792477c05b086170d18f7c8e70fbecb7905b2a29..bd9a20e8d4b494b50275693b568ef0004c48e75f 100644
--- a/sky/engine/core/painting/PaintingTasks.h
+++ b/sky/engine/core/painting/PaintingTasks.h
@@ -11,12 +11,13 @@
 namespace blink {
 class DisplayList;
 class Element;
+class Node;
 class PaintingCallback;
 
 class PaintingTasks {
 public:
     static void enqueueRequest(PassRefPtr<Element>, PassOwnPtr<PaintingCallback>);
-    static void enqueueCommit(PassRefPtr<Element>, PassRefPtr<DisplayList>);
+    static void enqueueCommit(PassRefPtr<Node>, PassRefPtr<DisplayList>);
 
     static bool serviceRequests();
     static void drainCommits();