cc::Fix computation of surface backfacing-ness when using property trees

Property trees currently use the owning layer's draw transform to
compute the render surface's backfacing-ness. This computation is
flawed as the owning layer's draw transform computed using property
trees has only the sublayer scale and not the transform to target. So,
we should use the surface's draw transform instead. This change also
fixes the unit test,
LayerTreeHostCommonTest.DoNotIncludeBackfaceInvisibleSurfaces when we
enable impl-thread property trees.

BUG=551629
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1430353002

Cr-Commit-Position: refs/heads/master@{#358736}

1 files changed, 13 insertions, 8 deletions

diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index 345182c..832f864 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -1776,13 +1776,16 @@ static void CalculateDrawPropertiesInternal(
     DCHECK(layer->render_surface());
     // Check back-face visibility before continuing with this surface and its
     // subtree
+    RenderSurfaceImpl* render_surface = layer->render_surface();
     if (!layer->double_sided() &&
         IsSurfaceBackFaceVisible(layer, combined_transform)) {
+      gfx::Transform draw_transform = combined_transform;
+      draw_transform.Scale(1.0 / combined_transform_scales.x(),
+                           1.0 / combined_transform_scales.y());
+      render_surface->SetDrawTransform(draw_transform);
       return;
     }
 
-    RenderSurfaceImpl* render_surface = layer->render_surface();
-
     if (IsRootLayer(layer)) {
       // The root layer's render surface size is predetermined and so the root
       // layer can't directly support non-identity transforms.  It should just
@@ -2494,12 +2497,6 @@ void CalculateRenderSurfaceLayerListInternal(
 
   if (render_to_separate_surface) {
     DCHECK(layer->render_surface());
-    if (!layer->double_sided() &&
-        IsSurfaceBackFaceVisible(layer, layer->draw_transform())) {
-      layer->ClearRenderSurfaceLayerList();
-      layer->draw_properties().render_target = nullptr;
-      return;
-    }
 
     if (use_property_trees) {
       RenderSurfaceDrawProperties draw_properties;
@@ -2520,6 +2517,14 @@ void CalculateRenderSurfaceLayerListInternal(
       layer->render_surface()->SetClipRect(draw_properties.clip_rect);
     }
 
+    if (!layer->double_sided() &&
+        IsSurfaceBackFaceVisible(layer,
+                                 layer->render_surface()->draw_transform())) {
+      layer->ClearRenderSurfaceLayerList();
+      layer->draw_properties().render_target = nullptr;
+      return;
+    }
+
     if (IsRootLayer(layer)) {
       // The root surface does not contribute to any other surface, it has no
       // target.