Let Range::expand not crash when Range's start node is not connected to document.

third_party/WebKit/Source/core/dom/Range.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Gunnstein Lye (gunnstein@netcom.no)
  * (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
  * (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2011 Motorola Mobility. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1626 matching lines @@
   DCHECK_EQ(oldNode.document(), m_ownerDocument);
   DCHECK(oldNode.parentNode());
   DCHECK(oldNode.nextSibling());
   DCHECK(oldNode.nextSibling()->isTextNode());
   boundaryTextNodeSplit(m_start, oldNode);
   boundaryTextNodeSplit(m_end, oldNode);
   DCHECK(boundaryPointsValid());
 }
 
 void Range::expand(const String& unit, ExceptionState& exceptionState) {
+  if (!startPosition().isConnected() || !endPosition().isConnected())
+    return;
   m_ownerDocument->updateStyleAndLayoutIgnorePendingStylesheets();
-
   VisiblePosition start = createVisiblePosition(startPosition());
   VisiblePosition end = createVisiblePosition(endPosition());
   if (unit == "word") {
     start = startOfWord(start);
     end = endOfWord(end);
   } else if (unit == "sentence") {
     start = startOfSentence(start);
     end = endOfSentence(end);
   } else if (unit == "block") {
     start = startOfParagraph(start);
@@ skipping 142 matching lines @@
                      .data()
               << "start offset: " << range->startOffset()
               << ", end offset: " << range->endOffset();
   } else {
     LOG(INFO) << "Cannot show tree if range is null, or if boundary points are "
                  "invalid.";
   }
 }
 
 #endif