Make the code compile on Mac OS X

src/isolate.h

 // Copyright 2010 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 278 matching lines @@
   V(Object*, string_stream_current_security_token, NULL)                       \
   /* TODO(isolates): Release this on destruction? */                           \
   V(int*, irregexp_interpreter_backtrack_stack_cache, NULL)                    \
   /* Serializer state. */                                                      \
   V(ExternalReferenceTable*, external_reference_table, NULL)                   \
   ISOLATE_PLATFORM_INIT_LIST(V)                                                \
   ISOLATE_LOGGING_INIT_LIST(V)                                                 \
   ISOLATE_DEBUGGER_INIT_LIST(V)
 
 class Isolate {
+  // These forward declarations are required to make the friend declarations in
+  // PerIsolateThreadData work on some older versions of gcc.
+  class ThreadDataTable;
+  class EntryStackItem;
  public:
   ~Isolate();
 
   typedef int ThreadId;
 
   // A thread has a PerIsolateThreadData instance for each isolate that it has
   // entered. That instance is allocated when the isolate is initially entered
   // and reused on subsequent entries.
   class PerIsolateThreadData {
    public:
@@ skipping 865 matching lines @@
 #define ISOLATED_CLASS class
 
 } }  // namespace v8::internal
 
 // TODO(isolates): Get rid of these -inl.h includes and place them only where
 //                 they're needed.
 #include "allocation-inl.h"
 #include "zone-inl.h"
 
 #endif  // V8_ISOLATE_H_