[Isolates] Avoid isolate lookup in HandleScope destructor.

include/v8.h

 // Copyright 2007-2009 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 452 matching lines @@
   void* operator new(size_t size);
   void operator delete(void*, size_t);
 
   // This Data class is accessible internally as HandleScopeData through a
   // typedef in the ImplementationUtilities class.
   class V8EXPORT Data {
    public:
     int extensions;
     internal::Object** next;
     internal::Object** limit;
-    inline void Initialize() {
+    internal::Isolate* isolate;
+    inline void Initialize(internal::Isolate* i) {

[Dmitry Titov, 2010/09/29 22:14:47]

Tiny nit, to consider, but I'm 50-50 on it myself:

It feels that Initialize is used more like "Reset" (at least in api.cc).

If the Data had a constructor taking Isolate*, then we could remove call to
Initialize from isolate.cc and don't do change in api.cc.

[Vitaly Repeshko, 2010/10/01 17:16:49]

When Data is used in an API HandleScope it can't be constructed with the right
arguments and stays uninitialized for a while. So it's more natural to
initialize it than to reset.

       extensions = -1;
       next = limit = NULL;
+      isolate = i;
     }
   };
 
   Data previous_;
 
   // Allow for the active closing of HandleScopes which allows to pass a handle
   // from the HandleScope being closed to the next top most HandleScope.
   bool is_closed_;
   internal::Object** RawClose(internal::Object** value);
 
@@ skipping 3286 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_