WebKit side of merge from r41149 to r41181.

JavaScriptCore/runtime/JSString.h

 /*
  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
  *  Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple 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 42 matching lines @@
     JSString* jsNontrivialString(ExecState*, const char*);
 
     // Should be used for strings that are owned by an object that will
     // likely outlive the JSValue this makes, such as the parse tree or a
     // DOM object that contains a UString
     JSString* jsOwnedString(JSGlobalData*, const UString&); 
     JSString* jsOwnedString(ExecState*, const UString&); 
 
     class JSString : public JSCell {
         friend class JIT;
-        friend class Interpreter;
+        friend class VPtrSet;
 
     public:
         JSString(JSGlobalData* globalData, const UString& value)
             : JSCell(globalData->stringStructure.get())
             , m_value(value)
         {
             Heap::heap(this)->reportExtraMemoryCost(value.cost());
         }
 
         enum HasOtherOwnerType { HasOtherOwner };
@@ skipping 121 matching lines @@
     ALWAYS_INLINE bool JSString::getStringPropertySlot(ExecState* exec, unsigned propertyName, PropertySlot& slot)
     {
         if (propertyName < static_cast<unsigned>(m_value.size())) {
             slot.setValue(jsSingleCharacterSubstring(exec, m_value, propertyName));
             return true;
         }
 
         return false;
     }
 
+    inline bool isJSString(JSGlobalData* globalData, JSValuePtr v) { return v.isCell() && v.asCell()->vptr() == globalData->jsStringVPtr; }
+
     // --- JSValue inlines ----------------------------
 
     inline JSString* JSValuePtr::toThisJSString(ExecState* exec)
     {
         return JSImmediate::isImmediate(asValue()) ? jsString(exec, JSImmediate::toString(asValue())) : asCell()->toThisJSString(exec);
     }
 
 } // namespace JSC
 
 #endif // JSString_h