Clip the start position when performing SVG text queries

Source/core/rendering/svg/SVGTextQuery.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010-2012. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 123 matching lines @@
 
     return false;
 }
 
 bool SVGTextQuery::mapStartEndPositionsIntoFragmentCoordinates(Data* queryData, const SVGTextFragment& fragment, int& startPosition, int& endPosition) const
 {
     // Reuse the same logic used for text selection & painting, to map our query start/length into start/endPositions of the current text fragment.
     startPosition -= queryData->processedCharacters;
     endPosition -= queryData->processedCharacters;
 
-    if (startPosition >= endPosition || startPosition < 0 || endPosition < 0)
+    startPosition = max(0, startPosition);
+
+    if (startPosition >= endPosition)
         return false;
 
     modifyStartEndPositionsRespectingLigatures(queryData, startPosition, endPosition);
     if (!queryData->textBox->mapStartEndPositionsIntoFragmentCoordinates(fragment, startPosition, endPosition))
         return false;
 
     ASSERT(startPosition < endPosition);
     return true;
 }
 
@@ skipping 384 matching lines @@
         return -1;
 
     CharacterNumberAtPositionData data(position);
     if (!executeQuery(&data, &SVGTextQuery::characterNumberAtPositionCallback))
         return -1;
 
     return data.processedCharacters;
 }
 
 }