Fixes for re-enabling more MSVC level 4 warnings: Source/core/ edition

Source/core/editing/TextIterator.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 912 matching lines @@
 }
 
 static bool shouldEmitNewlineAfterNode(Node& node)
 {
     // FIXME: It should be better but slower to create a VisiblePosition here.
     if (!shouldEmitNewlinesBeforeAndAfterNode(node))
         return false;
     // Check if this is the very last renderer in the document.
     // If so, then we should not emit a newline.
     Node* next = &node;
-    while ((next = NodeTraversal::nextSkippingChildren(*next))) {
-        if (next->renderer())
+    do {
+        next = NodeTraversal::nextSkippingChildren(*next);
+        if (next && next->renderer())
             return true;
-    }
+    } while (next);
     return false;
 }
 
 static bool shouldEmitNewlineBeforeNode(Node& node)
 {
     return shouldEmitNewlinesBeforeAndAfterNode(node);
 }
 
 static bool shouldEmitExtraNewlineForNode(Node* node)
 {
@@ skipping 1267 matching lines @@
             resultEnd = collapseTo;
             return;
         }
     }
 
     CharacterIterator computeRangeIterator(inputStart, inputEnd, iteratorFlagsForFindPlainText);
     calculateCharacterSubrange(computeRangeIterator, matchStart, matchLength, resultStart, resultEnd);
 }
 
 }