Handle nested position:sticky elements

third_party/WebKit/Source/core/layout/LayoutObject.cpp

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index 35313327dd0657a44781f524fd4e155277da6f9e..6e3d0357e8ae4f0918ce6939fe38fa48a8dab4d6 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -2074,6 +2074,14 @@ void LayoutObject::mapLocalToAncestor(const LayoutBoxModelObject* ancestor,
   }
 
   LayoutSize containerOffset = offsetFromContainer(container);
+
+  // TODO(smcgruer): Don't include offsetForInFlowPosition in
+  // offsetFromContainer when IgnoreStickyOffset is set.
+  if (isBoxModelObject() && isStickyPositioned() &&
+      (mode & IgnoreStickyOffset)) {
+    containerOffset -= toLayoutBoxModelObject(this)->offsetForInFlowPosition();
+  }
+
   if (isLayoutFlowThread()) {
     // So far the point has been in flow thread coordinates (i.e. as if
     // everything in the fragmentation context lived in one tall single column).