Elements whose contents start with an astral Unicode symbol disappear when CSS `::first-letter` is …

Source/platform/fonts/shaping/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 194 matching lines @@
         } else if ((direction == RTL && currentCharacterIndex >= from)
             || (direction == LTR && currentCharacterIndex < to)) {
             addGlyphToBuffer(glyphBuffer, advanceSoFar, run->m_direction,
                 run->m_fontData.get(), glyphData);
             advanceSoFar += glyphData.advance;
         }
     }
     return advanceSoFar - initialAdvance;
 }
 
-static inline unsigned countGraphemesInCluster(const UChar* str,
-    unsigned strLength, uint16_t startIndex, uint16_t endIndex)
-{
-    if (startIndex > endIndex) {
-        uint16_t tempIndex = startIndex;
-        startIndex = endIndex;
-        endIndex = tempIndex;
-    }
-    uint16_t length = endIndex - startIndex;
-    ASSERT(static_cast<unsigned>(startIndex + length) <= strLength);
-    TextBreakIterator* cursorPosIterator = cursorMovementIterator(&str[startIndex], length);
-
-    int cursorPos = cursorPosIterator->current();
-    int numGraphemes = -1;
-    while (0 <= cursorPos) {
-        cursorPos = cursorPosIterator->next();
-        numGraphemes++;
-    }
-    return numGraphemes < 0 ? 0 : numGraphemes;
-}
-
 static inline void addEmphasisMark(GlyphBuffer* buffer,
     const GlyphData* emphasisData, FloatPoint glyphCenter,
     float midGlyphOffset)
 {
     ASSERT(buffer);
     ASSERT(emphasisData);
 
     const SimpleFontData* emphasisFontData = emphasisData->fontData;
     ASSERT(emphasisFontData);
 
@@ skipping 57 matching lines @@
                 addEmphasisMark(glyphBuffer, emphasisData, glyphCenter, advanceSoFar + glyphAdvanceX / 2);
             }
             advanceSoFar += glyphAdvanceX;
         } else if (isClusterEnd) {
             uint16_t clusterEnd;
             if (direction == RTL)
                 clusterEnd = currentCharacterIndex;
             else
                 clusterEnd = isRunEnd ? run->m_startIndex + run->m_numCharacters + runOffset : run->glyphToCharacterIndex(i + 1) + runOffset;
 
-            graphemesInCluster = countGraphemesInCluster(textRun.characters16(), textRun.charactersLength(), clusterStart, clusterEnd);
+            graphemesInCluster = countCharactersAndGraphemesInCluster(textRun.characters16(), textRun.charactersLength(), clusterStart, clusterEnd).graphemes;
             if (!graphemesInCluster || !clusterAdvance)
                 continue;
 
             float glyphAdvanceX = clusterAdvance / graphemesInCluster;
             for (unsigned j = 0; j < graphemesInCluster; ++j) {
                 // Do not put emphasis marks on space, separator, and control characters.
                 if (Character::canReceiveTextEmphasis(textRun[currentCharacterIndex]))
                     addEmphasisMark(glyphBuffer, emphasisData, glyphCenter, advanceSoFar + glyphAdvanceX / 2);
                 advanceSoFar += glyphAdvanceX;
             }
@@ skipping 830 matching lines @@
             return spacing;
     }
 
     // Don't need to check m_textRun.allowsTrailingExpansion() since it's covered by !m_expansionOpportunityCount above
     spacing += nextExpansionPerOpportunity();
     m_isAfterExpansion = true;
     return spacing;
 }
 
 } // namespace blink