[reland] SegmentedString::push() should always push a char in front

Source/core/html/parser/HTMLEntityParser.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
  * Copyright (C) 2010 Google, Inc. All Rights Reserved.
  *
  * 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.
@@ skipping 77 matching lines @@
     return 0;
 }
 
 typedef Vector<UChar, 64> ConsumedCharacterBuffer;
 
 static void unconsumeCharacters(SegmentedString& source, ConsumedCharacterBuffer& consumedCharacters)
 {
     if (consumedCharacters.size() == 1)
         source.push(consumedCharacters[0]);
     else if (consumedCharacters.size() == 2) {
+        source.push(consumedCharacters[1]);
         source.push(consumedCharacters[0]);
-        source.push(consumedCharacters[1]);
     } else
         source.prepend(SegmentedString(String(consumedCharacters)));
 }
 
 static bool consumeNamedEntity(SegmentedString& source, DecodedHTMLEntity& decodedEntity, bool& notEnoughCharacters, UChar additionalAllowedCharacter, UChar& cc)
 {
     ConsumedCharacterBuffer consumedCharacters;
     HTMLEntitySearch entitySearch;
     while (!source.isEmpty()) {
         cc = source.currentChar();
@@ skipping 95 matching lines @@
                 continue;
             }
             source.push('#');
             return false;
         }
         case MaybeHexLowerCaseX: {
             if (isHexDigit(cc)) {
                 entityState = Hex;
                 continue;
             }
+            source.push('x');
             source.push('#');
-            source.push('x');
             return false;
         }
         case MaybeHexUpperCaseX: {
             if (isHexDigit(cc)) {
                 entityState = Hex;
                 continue;
             }
+            source.push('X');
             source.push('#');
-            source.push('X');
             return false;
         }
         case Hex: {
             if (isHexDigit(cc)) {
                 if (result != kInvalidUnicode)
                     result = result * 16 + asHexDigit(cc);
             } else if (cc == ';') {
                 source.advanceAndASSERT(cc);
                 appendLegalEntityFor(result, decodedEntity);
                 return true;
@@ skipping 60 matching lines @@
     if (!search.isEntityPrefix())
         return 0;
 
     size_t numberOfCodePoints = appendUChar32ToUCharArray(search.mostRecentMatch()->firstValue, result);
     if (!search.mostRecentMatch()->secondValue)
         return numberOfCodePoints;
     return numberOfCodePoints + appendUChar32ToUCharArray(search.mostRecentMatch()->secondValue, result + numberOfCodePoints);
 }
 
 } // namespace blink