Move String::isSafeToSendToAnotherThread to StringImpl.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller ( mueller@kde.org )
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Andrew Wellington (proton@wiretapped.net)
  *
  * 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
@@ skipping 268 matching lines @@
     if (isAtomic())
         AtomicStringTable::instance().remove(this);
 }
 
 void StringImpl::destroyIfNotStatic()
 {
     if (!isStatic())
         delete this;
 }
 
+bool StringImpl::isSafeToSendToAnotherThread() const
+{
+    if (isStatic())
+        return true;
+    // AtomicStrings are not safe to send between threads as ~StringImpl()
+    // will try to remove them from the wrong AtomicStringTable.
+    if (isAtomic())
+        return false;
+    if (hasOneRef())
+        return true;
+    return false;
+}
+
 PassRefPtr<StringImpl> StringImpl::createUninitialized(unsigned length, LChar*& data)
 {
     if (!length) {
         data = 0;
         return empty();
     }
 
     // Allocate a single buffer large enough to contain the StringImpl
     // struct as well as the data which it contains. This removes one
     // heap allocation from this call.
@@ skipping 1705 matching lines @@
         } else if (localeIdMatchesLang(localeIdentifier, "lt")) {
             // TODO(rob.buis) implement upper-casing rules for lt
             // like in StringImpl::upper(locale).
         }
     }
 
     return toUpper(c);
 }
 
 } // namespace WTF