cc:: Add transform nodes at boundaries of 3d rendering contexts

cc/trees/property_tree.h

Index: cc/trees/property_tree.h
diff --git a/cc/trees/property_tree.h b/cc/trees/property_tree.h
index db0396d085fa78709fe7957b7d800d83416bf955..f16c33c4cd70854785cd9f06ff6a6138842dc676 100644
--- a/cc/trees/property_tree.h
+++ b/cc/trees/property_tree.h
@@ -118,6 +118,8 @@ struct CC_EXPORT TransformNodeData {
 
   bool needs_sublayer_scale : 1;
 
+  bool is_3d_sorted : 1;

[weiliangc, 2016/01/25 21:29:26]

Can we have 3d rendering context within 3d rendering context? Is bool sufficient
or do we need an id?

[ajuma, 2016/01/25 21:53:00]

Looking at PaintLayer::renderingContextRoot (the id is just a hash of this
value), it seems possible to have:
A->B->C where A and C preserve-3d but B doesn't, resulting in all layers being
3d sorted but A and B having a different id than C. So I think we need an id
here.

+
   // These are used to position nodes wrt the right or bottom of the inner or
   // outer viewport.
   bool affected_by_inner_viewport_bounds_delta_x : 1;