cc : Snap texture layers to pixel boundary

cc/trees/transform_node.h

Index: cc/trees/transform_node.h
diff --git a/cc/trees/transform_node.h b/cc/trees/transform_node.h
index 1e8c3910aaa08a8449e3a5136995e0f6661e04eb..a70312a03d2e53ba4b8f52d4c7b0172d2faae340 100644
--- a/cc/trees/transform_node.h
+++ b/cc/trees/transform_node.h
@@ -94,6 +94,8 @@ struct CC_EXPORT TransformNode {
 
   bool scrolls : 1;
 
+  bool should_be_snapped : 1;
+
   bool needs_surface_contents_scale : 1;
 
   // These are used to position nodes wrt the right or bottom of the inner or
@@ -120,9 +122,10 @@ struct CC_EXPORT TransformNode {
   // TODO(vollick): will be moved when accelerated effects are implemented.
   gfx::ScrollOffset scroll_offset;
 
-  // We scroll snap where possible, but this means fixed-pos elements must be
-  // adjusted.  This value stores the snapped amount for this purpose.
-  gfx::Vector2dF scroll_snap;
+  // This value stores the snapped amount whenever we snap. If the snap is due
+  // to a scroll, we need it to calculate fixed-pos elements adjustment, even
+  // otherwise we may need it to undo the snapping next frame.
+  gfx::Vector2dF snap_amount;
 
   // TODO(vollick): will be moved when accelerated effects are implemented.
   gfx::Vector2dF source_offset;