cc : Snap texture layers to pixel boundary

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 17ed191d074f8376327c66cc192f0c4267ff7e75..72528646e1507e7feae222c456f57ee34f163049 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -493,6 +493,7 @@ bool AddTransformNodeIfNeeded(
   const bool is_scrollable = layer->scrollable();
   const bool is_fixed = PositionConstraint(layer).is_fixed_position();
   const bool is_sticky = StickyPositionConstraint(layer).is_sticky;
+  const bool is_snapped = layer->IsSnapped();
 
   const bool has_significant_transform =
       !Transform(layer).IsIdentityOr2DTranslation();
@@ -523,7 +524,8 @@ bool AddTransformNodeIfNeeded(
   const bool is_at_boundary_of_3d_rendering_context =
       IsAtBoundaryOf3dRenderingContext(layer);
 
-  bool requires_node = is_root || is_scrollable || has_significant_transform ||
+  DCHECK(!is_scrollable || is_snapped);

[enne (OOO), 2016/10/26 20:32:33]

I wish we had DCHECK_IMPLIES.  :C

[jaydasika, 2016/10/26 21:49:14]

I wish that too. Just in this CL, I have 3 DCHECK(!a || b). DCHECK_IMPLIES is
easier to understand. 

+  bool requires_node = is_root || is_snapped || has_significant_transform ||
                        has_any_transform_animation || has_surface || is_fixed ||
                        is_page_scale_layer || is_overscroll_elasticity_layer ||
                        has_proxied_transform_related_property ||
@@ -599,6 +601,7 @@ bool AddTransformNodeIfNeeded(
       node->id;
 
   node->scrolls = is_scrollable;
+  node->should_be_snapped = is_snapped;
   node->flattens_inherited_transform = data_for_children->should_flatten;
 
   node->sorting_context_id = layer->sorting_context_id();