Handle zero width joiner in HarfBuzzShaper

Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp

 /*
  * Copyright (c) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 BlackBerry Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 599 matching lines @@
     UErrorCode errorCode = U_ZERO_ERROR;
     UScriptCode nextScript = uscript_getScript(character, &errorCode);
     if (U_FAILURE(errorCode))
         return false;
 
     do {
         const UChar* currentCharacterPosition = iterator.characters();
         const SimpleFontData* currentFontData = nextFontData;
         UScriptCode currentScript = nextScript;
 
+        UChar32 lastCharacter = character;
         for (iterator.advance(clusterLength); iterator.consume(character, clusterLength); iterator.advance(clusterLength)) {
             if (Character::treatAsZeroWidthSpace(character))
                 continue;
 
             int length = handleMultipleUChar(character, clusterLength, currentFontData, currentCharacterPosition, iterator.characters() + clusterLength, normalizedBufferEnd);
             if (length) {
                 clusterLength = length;
                 continue;
             }
 
             nextFontData = font->glyphDataForCharacter(character, false).fontData;
             nextScript = uscript_getScript(character, &errorCode);
             if (U_FAILURE(errorCode))
                 return false;
+            if (lastCharacter == zeroWidthJoiner)
+                currentFontData = nextFontData;
             if ((nextFontData != currentFontData) || ((currentScript != nextScript) && (nextScript != USCRIPT_INHERITED) && (!uscript_hasScript(character, currentScript))))
                 break;
             currentCharacterPosition = iterator.characters();
+            lastCharacter = character;
         }
 
         CandidateRun run = { character, startIndexOfCurrentRun, iterator.currentCharacter(), currentFontData, currentScript };
         runs->append(run);
 
         currentFontData = nextFontData;
         startIndexOfCurrentRun = iterator.currentCharacter();
     } while (iterator.consume(character, clusterLength));
 
     return true;
@@ skipping 382 matching lines @@
     if (!foundToX)
         toX = m_run.rtl() ? 0 : m_totalWidth;
 
     // Using floorf() and roundf() as the same as mac port.
     if (fromX < toX)
         return FloatRect(floorf(point.x() + fromX), point.y(), roundf(toX - fromX), height);
     return FloatRect(floorf(point.x() + toX), point.y(), roundf(fromX - toX), height);
 }
 
 } // namespace WebCore