Move String::isSafeToSendToAnotherThread to StringImpl.

third_party/WebKit/Source/wtf/text/StringImpl.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2009 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 206 matching lines @@
     size_t charactersSizeInBytes() const
     {
         return length() * (is8Bit() ? sizeof(LChar) : sizeof(UChar));
     }
 
     bool isAtomic() const { return m_isAtomic; }
     void setIsAtomic(bool isAtomic) { m_isAtomic = isAtomic; }
 
     bool isStatic() const { return m_isStatic; }
 
+    bool isSafeToSendToAnotherThread() const;
+
     // The high bits of 'hash' are always empty, but we prefer to store our
     // flags in the low bits because it makes them slightly more efficient to
     // access.  So, we shift left and right when setting and getting our hash
     // code.
     void setHash(unsigned hash) const
     {
         DCHECK(!hasHash());
         // Multiple clients assume that StringHasher is the canonical string
         // hash function.
         DCHECK(hash == (is8Bit() ? StringHasher::computeHashAndMaskTop8Bits(characters8(), m_length) : StringHasher::computeHashAndMaskTop8Bits(characters16(), m_length)));
@@ skipping 458 matching lines @@
 using WTF::TextCaseASCIIInsensitive;
 using WTF::TextCaseInsensitive;
 using WTF::TextCaseSensitive;
 using WTF::TextCaseSensitivity;
 using WTF::equal;
 using WTF::equalNonNull;
 using WTF::lengthOfNullTerminatedString;
 using WTF::reverseFind;
 
 #endif