Fix some edge cases

Bug: 27709981

This desperately needs a refactor, but to keep
the current (really needed & nice) behavior of
dispatching after sync finishes would be difficult
to handle cleanly without lots of ripping so... #yolo

Change-Id: I831a06c6ae7412a062720d68ecbe3085190f0258
diff --git a/libs/hwui/RenderNode.h b/libs/hwui/RenderNode.h
index b0136cf..acdc3d8 100644
--- a/libs/hwui/RenderNode.h
+++ b/libs/hwui/RenderNode.h
@@ -117,7 +117,7 @@
 
     void debugDumpLayers(const char* prefix);
 
-    ANDROID_API void setStagingDisplayList(DisplayList* newData);
+    ANDROID_API void setStagingDisplayList(DisplayList* newData, TreeObserver* observer);
 
     void computeOrdering();