[simulator] Make reference redirection thread-safe.

src/assembler.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 800 matching lines @@
     DIRECT_GETTER_CALL,
 
     // Call to accessor getter callback via InvokeAccessorGetterCallback.
     // void f(Local<Name> property, PropertyCallbackInfo& info,
     //     AccessorNameGetterCallback callback)
     PROFILING_GETTER_CALL
   };
 
   static void SetUp();
 
+  // These functions must use the isolate in a thread-safe way.
   typedef void* ExternalReferenceRedirector(Isolate* isolate, void* original,
                                             Type type);
 
   ExternalReference() : address_(NULL) {}
 
   ExternalReference(Address address, Isolate* isolate);
 
   ExternalReference(ApiFunction* ptr, Type type, Isolate* isolate);
 
   ExternalReference(Builtins::Name name, Isolate* isolate);
@@ skipping 423 matching lines @@
     std::vector<ConstantPoolEntry> shared_entries;
   };
 
   Label emitted_label_;  // Records pc_offset of emitted pool
   PerTypeEntryInfo info_[ConstantPoolEntry::NUMBER_OF_TYPES];
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_ASSEMBLER_H_