Change handling of unmatched surrogate pairs

Source/platform/fonts/UTF16TextIterator.cpp

 /*
  * Copyright (C) 2003, 2006, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Holger Hans Peter Freyther
  * Copyright (C) Research In Motion Limited 2011. 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 30 matching lines @@
 
 UTF16TextIterator::UTF16TextIterator(const UChar* characters, int currentCharacter, int endOffset, int endCharacter)
     : m_characters(characters)
     , m_charactersEnd(characters + (endCharacter - currentCharacter))
     , m_offset(currentCharacter)
     , m_endOffset(endOffset)
     , m_currentGlyphLength(0)
 {
 }
 
-bool UTF16TextIterator::consumeSurrogatePair(UChar32& character)
+bool UTF16TextIterator::isValidSurrogatePair(UChar32& character)
 {
-    if (!U16_IS_SURROGATE(character))
-        return true;
-
     // If we have a surrogate pair, make sure it starts with the high part.
     if (!U16_IS_SURROGATE_LEAD(character))
         return false;
 
     // Do we have a surrogate pair? If so, determine the full Unicode (32 bit)
     // code point before glyph lookup.
     // Make sure we have another character and it's a low surrogate.
     if (m_characters + 1 >= m_charactersEnd)
         return false;
 
     UChar low = m_characters[1];
     if (!U16_IS_TRAIL(low))
         return false;
+    return true;
+}
 
+bool UTF16TextIterator::consumeSurrogatePair(UChar32& character)
+{
+    if (!U16_IS_SURROGATE(character))
+        return true;
+
+    if (!isValidSurrogatePair(character)) {
+        character = replacementCharacter;
+        return true;
+    }
+
+    UChar low = m_characters[1];
     character = U16_GET_SUPPLEMENTARY(character, low);
     m_currentGlyphLength = 2;
     return true;
 }
 
 void UTF16TextIterator::consumeMultipleUChar()
 {
     const UChar* markCharactersEnd = m_characters + m_currentGlyphLength;
     int markLength = m_currentGlyphLength;
     while (markCharactersEnd < m_charactersEnd) {
         UChar32 nextCharacter;
         int nextCharacterLength = 0;
         U16_NEXT(markCharactersEnd, nextCharacterLength,
             m_charactersEnd - markCharactersEnd, nextCharacter);
         if (!(U_GET_GC_MASK(nextCharacter) & U_GC_M_MASK))
             break;
         markLength += nextCharacterLength;
         markCharactersEnd += nextCharacterLength;
     }
     m_currentGlyphLength = markLength;
 }
 
 }