offsetParent() fails to consider continuations when searching for the parent.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved.
  *               (http://www.torchmobile.com/)
@@ skipping 3199 matching lines @@
     return nullptr;
 
   float effectiveZoom = style()->effectiveZoom();
   Node* node = nullptr;
   for (LayoutObject* ancestor = parent(); ancestor;
        ancestor = ancestor->parent()) {
     // Spec: http://www.w3.org/TR/cssom-view/#offset-attributes
 
     node = ancestor->node();
 
-    if (!node)
-      continue;
+    if (!node) {
+      if (!ancestor->virtualContinuation())
+        continue;
+
+      // This is an anonymous continuation; ie. our ancestor is really the split
+      // inline. Find it by spooling to the end of the continuation chain.
+
+      while (LayoutBoxModelObject* cont = ancestor->virtualContinuation())
+        ancestor = cont;
+
+      node = ancestor->node();
+
+      DCHECK(node);
+    }
 
     // TODO(kochi): If |base| or |node| is nested deep in shadow roots, this
     // loop may get expensive, as isUnclosedNodeOf() can take up to O(N+M) time
     // (N and M are depths).
     if (base &&
         (node->isClosedShadowHiddenFrom(*base) ||
          (node->isInShadowTree() &&
           node->containingShadowRoot()->type() == ShadowRootType::UserAgent))) {
       // If 'position: fixed' node is found while traversing up, terminate the
       // loop and return null.
@@ skipping 325 matching lines @@
     const blink::LayoutObject* root = object1;
     while (root->parent())
       root = root->parent();
     root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
   } else {
     WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
   }
 }
 
 #endif