No default value for AncestorSearchConstraint in locateFlowThreadContainingBlockOf().

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 669 matching lines @@
   }
 
   return nullptr;
 }
 
 LayoutFlowThread* LayoutObject::locateFlowThreadContainingBlock() const {
   ASSERT(isInsideFlowThread());
 
   // See if we have the thread cached because we're in the middle of layout.
   if (LayoutState* layoutState = view()->layoutState()) {
+    // TODO(mstensho): We should really just return whatever
+    // layoutState->flowThread() returns here, also if the value is nullptr.
     if (LayoutFlowThread* flowThread = layoutState->flowThread())
       return flowThread;
   }
 
   // Not in the middle of layout so have to find the thread the slow way.
-  return LayoutFlowThread::locateFlowThreadContainingBlockOf(*this);
+  return LayoutFlowThread::locateFlowThreadContainingBlockOf(
+      *this, LayoutFlowThread::AnyAncestor);
 }
 
 static inline bool objectIsRelayoutBoundary(const LayoutObject* object) {
   // FIXME: In future it may be possible to broaden these conditions in order to
   // improve performance.
   if (object->isTextControl())
     return true;
 
   if (object->isSVGRoot())
     return true;
@@ skipping 2919 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