Add ClipNode when Render Surface Inherits Clip

cc/trees/property_tree_builder.cc

Index: cc/trees/property_tree_builder.cc
diff --git a/cc/trees/property_tree_builder.cc b/cc/trees/property_tree_builder.cc
index 8ad44070ec7ffdf6d648c6356e6673153b9366d3..d9794fcddce501480e1230aba78c20973607a61e 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -79,6 +79,9 @@ static bool RequiresClipNode(LayerType* layer,
   if (!render_surface_applies_clip)
     return false;
 
+  if (!layer->transform().IsFlat())

[ajuma, 2015/08/04 15:37:19]

What if the transform is animated, and becomes non-flat on the compositor thread
(after tree creation)? How about just unconditionally creating a node if we
reach this point (and then we can get rid of the axis-alignment logic below)?

[jaydasika, 2015/08/04 15:38:53]

That breaks a lot of unit tests.

[ajuma, 2015/08/04 15:40:26]

It'd be good to understand why (since if there's something incorrect about that,
there might also be something incorrect about the non-flat case too, but we
maybe we just don't have that many unit tests with non-flat transforms).

+    return true;
+
   bool axis_aligned_with_respect_to_parent =
       data.transform_tree->Are2DAxisAligned(layer->transform_tree_index(),
                                             parent_transform_id);
@@ -122,7 +125,7 @@ void AddClipNodeIfNeeded(const DataForRecursion<LayerType>& data_from_ancestor,
     parent_id = 0;
 
   if (!RequiresClipNode(layer, data_from_ancestor, parent->data.transform_id,
-                        data_for_children->ancestor_clips_subtree)) {
+                        ancestor_clips_subtree)) {
     // Unclipped surfaces reset the clip rect.
     data_for_children->clip_tree_parent = parent_id;
   } else {
@@ -138,6 +141,9 @@ void AddClipNodeIfNeeded(const DataForRecursion<LayerType>& data_from_ancestor,
     node.data.target_id =
         data_for_children->render_target->transform_tree_index();
     node.owner_id = layer->id();
+    node.data.inherit_parent_target_space_clip =
+        !data_for_children->ancestor_clips_subtree &&
+        layer->has_render_surface() && ancestor_clips_subtree;
 
     data_for_children->clip_tree_parent =
         data_for_children->clip_tree->Insert(node, parent_id);