Fix nested 'unicode-bidi: isolate' can cause infinite loop

Source/core/layout/line/InlineIterator.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010 Apple Inc. All right reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 514 matching lines @@
 
 static inline LineLayoutItem highestContainingIsolateWithinRoot(LineLayoutItem object, LineLayoutItem root)
 {
     ASSERT(object);
     LineLayoutItem containingIsolateObj = 0;
     while (object && object != root) {
         if (isIsolatedInline(object))
             containingIsolateObj = object;
 
         object = object.parent();
+        ASSERT(object);
     }
     return containingIsolateObj;
 }
 
 static inline unsigned numberOfIsolateAncestors(const InlineIterator& iter)
 {
     LineLayoutItem object = iter.object();
     if (!object)
         return 0;
     unsigned count = 0;
@@ skipping 196 matching lines @@
         m_sor = m_eor;
     }
 
     m_direction = WTF::Unicode::OtherNeutral;
     m_status.eor = WTF::Unicode::OtherNeutral;
 }
 
 }
 
 #endif // InlineIterator_h