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 d06a1caa1e8eeb00b209db861ca386bb3eadde08..33ba14784cca28fca01a807ede5074541bd9b565 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -2073,6 +2073,14 @@ 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).