cc: Always use invalidation on the pending tree when deciding to share

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 e51821fbc92a7d2b8f13536998b41210f141003d..2dc0724c9e8fbd368dc85c94fb7f07ccf0e98fa3 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -632,8 +632,13 @@ PicturePileImpl* PictureLayerImpl::GetPile() {
   return pile_.get();
 }
 
-const Region* PictureLayerImpl::GetInvalidation() {
-  return &invalidation_;
+const Region* PictureLayerImpl::GetPendingInvalidation() {
+  if (layer_tree_impl()->IsPendingTree())
+    return &invalidation_;
+  DCHECK(layer_tree_impl()->IsActiveTree());
+  if (PictureLayerImpl* twin_layer = GetTwinLayer())
+    return &twin_layer->invalidation_;
+  return nullptr;
 }
 
 const PictureLayerTiling* PictureLayerImpl::GetTwinTiling(