cc: Fix screen-space transform flattening in CalcDrawProps

cc/trees/layer_tree_host_common.cc

Index: cc/trees/layer_tree_host_common.cc
diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index f4c2029e7fa19263f98ecc67ac2806fc0924d5e8..9059ae1c0021097639768269fc38115190b63101 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -1816,8 +1816,6 @@ static void CalculateDrawPropertiesInternal(
   // layer's "screen space" and local content space.
   layer_draw_properties.screen_space_transform =
       data_from_ancestor.full_hierarchy_matrix;
-  if (layer->should_flatten_transform())
-    layer_draw_properties.screen_space_transform.FlattenTo2d();
   layer_draw_properties.screen_space_transform.PreconcatTransform
       (layer_draw_properties.target_space_transform);
 
@@ -1936,6 +1934,10 @@ static void CalculateDrawPropertiesInternal(
     data_for_children.full_hierarchy_matrix.PreconcatTransform(
         render_surface->draw_transform());
 
+    // A render surface inherently acts as a flattening point for the content of
+    // its descendants.
+    data_for_children.full_hierarchy_matrix.FlattenTo2d();
+
     if (layer->mask_layer()) {
       DrawProperties<LayerType>& mask_layer_draw_properties =
           layer->mask_layer()->draw_properties();