cc: Change how/when we build layer list/property tress in tests.

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 0adf8745e1a6e80207f614dd9b878cbd973c8794..412f92c31ee2d3b8a14a3bacc2b9d653b9a1eb7e 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -265,9 +265,11 @@ void LayerTreeImpl::SetRootLayerForTesting(std::unique_ptr<LayerImpl> layer) {
   if (root_layer_for_testing_ && layer.get() != root_layer_for_testing_)
     RemoveLayer(root_layer_for_testing_->id());
   root_layer_for_testing_ = layer.get();
-  if (layer)
+  ClearLayerList();
+  if (layer) {
     AddLayer(std::move(layer));
-  BuildLayerListForTesting();
+    BuildLayerListForTesting();
+  }
   layer_tree_host_impl_->OnCanDrawStateChangedForTree();
 }
 
@@ -1024,6 +1026,7 @@ void LayerTreeImpl::BuildLayerListAndPropertyTreesForTesting() {
   BuildLayerListForTesting();
   PropertyTreeBuilder::PreCalculateMetaInformationForTesting(
       root_layer_for_testing_);
+  property_trees_.needs_rebuild = true;
   property_trees_.transform_tree.set_source_to_parent_updates_allowed(true);
   PropertyTreeBuilder::BuildPropertyTrees(
       root_layer_for_testing_, PageScaleLayer(), InnerViewportScrollLayer(),
@@ -1035,6 +1038,20 @@ void LayerTreeImpl::BuildLayerListAndPropertyTreesForTesting() {
   property_trees_.transform_tree.set_source_to_parent_updates_allowed(false);
 }
 
+void LayerTreeImpl::BuildPropertyTreesForTesting() {
+  PropertyTreeBuilder::PreCalculateMetaInformationForTesting(layer_list_[0]);
+  property_trees_.needs_rebuild = true;
+  property_trees_.transform_tree.set_source_to_parent_updates_allowed(true);
+  PropertyTreeBuilder::BuildPropertyTrees(
+      layer_list_[0], PageScaleLayer(), InnerViewportScrollLayer(),
+      OuterViewportScrollLayer(), OverscrollElasticityLayer(),
+      elastic_overscroll()->Current(IsActiveTree()),
+      current_page_scale_factor(), device_scale_factor(),
+      gfx::Rect(DrawViewportSize()), layer_tree_host_impl_->DrawTransform(),
+      &property_trees_);
+  property_trees_.transform_tree.set_source_to_parent_updates_allowed(false);
+}
+
 const LayerImplList& LayerTreeImpl::RenderSurfaceLayerList() const {
   // If this assert triggers, then the list is dirty.
   DCHECK(!needs_update_draw_properties_);