cc: Add a flag to layers that returns true if the layer is in RSLL.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 36e754fb762618f9a364e7ab07d76e5f1df949d0..42900562d1d1a1af500eedce9f1dfa3e305a9d85 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -347,10 +347,16 @@ void PictureLayerImpl::AppendQuads(QuadSink* quad_sink,
 }
 
 void PictureLayerImpl::DidUnregisterLayer() {
+  TRACE_EVENT0("cc", "PictureLayerImpl::DidUnregisterLayer");
+
   layer_needs_to_register_itself_ = true;
+  RemoveAllTilings();
 }
 
 void PictureLayerImpl::UpdateTilePriorities() {
+  TRACE_EVENT0("cc", "PictureLayerImpl::UpdateTilePriorities");
+
+  DCHECK(IsDrawnRenderSurfaceLayerListMember());
   DCHECK(!needs_post_commit_initialization_);
   CHECK(should_update_tile_priorities_);