Handle nested position:sticky elements

cc/blink/web_layer_impl.cc

Index: cc/blink/web_layer_impl.cc
diff --git a/cc/blink/web_layer_impl.cc b/cc/blink/web_layer_impl.cc
index 73e62b3e66fc0f018aa19bf2484402d08a1b69af..ad60d0cf7fbc79934eb15ef4fc0e6e89c3e9620f 100644
--- a/cc/blink/web_layer_impl.cc
+++ b/cc/blink/web_layer_impl.cc
@@ -398,6 +398,15 @@ static cc::LayerStickyPositionConstraint ToStickyPositionConstraint(
       web_constraint.scrollContainerRelativeStickyBoxRect;
   constraint.scroll_container_relative_containing_block_rect =
       web_constraint.scrollContainerRelativeContainingBlockRect;
+  constraint.nearest_sticky_element_shifting_sticky_box =
+      web_constraint.nearestStickyElementShiftingStickyBox
+          ? web_constraint.nearestStickyElementShiftingStickyBox->ccLayer()
+          : nullptr;
+  constraint.nearest_sticky_element_shifting_containing_block =
+      web_constraint.nearestStickyElementShiftingContainingBlock
+          ? web_constraint.nearestStickyElementShiftingContainingBlock
+                ->ccLayer()
+          : nullptr;
   return constraint;
 }
 void WebLayerImpl::setStickyPositionConstraint(