Transforming PersistentHandleVisitor to not need to copy Persistent handles.

src/api.cc

 // Copyright 2012 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 5086 matching lines @@
 
 
 class VisitorAdapter : public i::ObjectVisitor {
  public:
   explicit VisitorAdapter(PersistentHandleVisitor* visitor)
       : visitor_(visitor) {}
   virtual void VisitPointers(i::Object** start, i::Object** end) {
     UNREACHABLE();
   }
   virtual void VisitEmbedderReference(i::Object** p, uint16_t class_id) {
+#ifdef V8_USE_OLD_STYLE_PERSISTENT_HANDLE_VISITORS
     visitor_->VisitPersistentHandle(ToApi<Value>(i::Handle<i::Object>(p)),
                                     class_id);
+#else
+    Value* value = ToApi<Value>(i::Handle<i::Object>(p));
+    visitor_->VisitPersistentHandle(
+        reinterpret_cast<Persistent<Value>*>(&value), class_id);
+#endif
   }
  private:
   PersistentHandleVisitor* visitor_;
 };
 
 
 void v8::V8::VisitHandlesWithClassIds(PersistentHandleVisitor* visitor) {
   i::Isolate* isolate = i::Isolate::Current();
   IsDeadCheck(isolate, "v8::V8::VisitHandlesWithClassId");
 
@@ skipping 2784 matching lines @@
 
   v->VisitPointers(blocks_.first(), first_block_limit_);
 
   for (int i = 1; i < blocks_.length(); i++) {
     v->VisitPointers(blocks_[i], &blocks_[i][kHandleBlockSize]);
   }
 }
 
 
 } }  // namespace v8::internal