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

Source/platform/text/TextBreakIterator.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007-2009 Torch Mobile, Inc.
  * Copyright (C) 2011 Google Inc. 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 32 matching lines @@
     NonSharedCharacterBreakIterator it(string);
     if (!it)
         return stringLength;
 
     unsigned num = 0;
     while (it.next() != TextBreakDone)
         ++num;
     return num;
 }
 
+ClusterData countCharactersAndGraphemesInCluster(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 ClusterData(std::max(numGraphemes, 0), cursorPosIterator->current());
+}
 
 static inline bool isBreakableSpace(UChar ch)
 {
     switch (ch) {
     case ' ':
     case '\n':
     case '\t':
         return true;
     default:
         return false;
@@ skipping 224 matching lines @@
 }
 
 int LazyLineBreakIterator::nextBreakablePositionKeepAll(int pos)
 {
     if (m_string.is8Bit())
         return nextBreakablePosition<LChar>(*this, m_string.characters8(), m_string.length(), pos);
     return nextBreakablePositionKeepAllInternal(*this, m_string.characters16(), m_string.length(), pos);
 }
 
 } // namespace blink