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

Source/platform/fonts/shaping/HarfBuzzShaper.cpp

Index: Source/platform/fonts/shaping/HarfBuzzShaper.cpp
diff --git a/Source/platform/fonts/shaping/HarfBuzzShaper.cpp b/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
index 44fcb3245b14168d38ef1e73f4016025a5fbcc78..c32f25889a734dff979e763cfdea3a365d93bd51 100644
--- a/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
+++ b/Source/platform/fonts/shaping/HarfBuzzShaper.cpp
@@ -215,26 +215,6 @@ static inline float harfBuzzPositionToFloat(hb_position_t value)
     return static_cast<float>(value) / (1 << 16);
 }
 
-static inline unsigned countGraphemesInCluster(const UChar* normalizedBuffer, unsigned normalizedBufferLength, 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) <= normalizedBufferLength);
-    TextBreakIterator* cursorPosIterator = cursorMovementIterator(&normalizedBuffer[startIndex], length);
-
-    int cursorPos = cursorPosIterator->current();
-    int numGraphemes = -1;
-    while (0 <= cursorPos) {
-        cursorPos = cursorPosIterator->next();
-        numGraphemes++;
-    }
-    return numGraphemes < 0 ? 0 : numGraphemes;
-}
-
 inline HarfBuzzShaper::HarfBuzzRun::HarfBuzzRun(const SimpleFontData* fontData, unsigned startIndex, unsigned numCharacters, hb_direction_t direction, hb_script_t script)
     : m_fontData(fontData)
     , m_startIndex(startIndex)
@@ -1076,7 +1056,7 @@ float HarfBuzzShaper::fillGlyphBufferForTextEmphasis(GlyphBuffer* glyphBuffer, H
             else
                 clusterEnd = isRunEnd ? currentRun->startIndex() + currentRun->numCharacters() : currentRun->glyphToCharacterIndex(i + 1);
 
-            graphemesInCluster = countGraphemesInCluster(m_normalizedBuffer.get(), m_normalizedBufferLength, clusterStart, clusterEnd);
+            graphemesInCluster = countCharactersAndGraphemesInCluster(m_normalizedBuffer.get(), m_normalizedBufferLength, clusterStart, clusterEnd).graphemes;
             if (!graphemesInCluster || !clusterAdvance)
                 continue;