Implemented lazy sweeping of new space.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index f25112939cada014a807e9c7c35d2d61d8230a75..4414a757cca9326e9ca37b05abf947a2b3636b6f 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1249,6 +1249,14 @@ void HeapObject::IteratePointer(ObjectVisitor* v, int offset) {
 }
 
 
+void HeapObject::ClearDeadObject() {
+  Address& map_field = Memory::Address_at(address());
+  if (GetHeap()->map_space()->Contains(map_field)) {
+    map_field = NULL;
+  }
+}
+
+
 double HeapNumber::value() {
   return READ_DOUBLE_FIELD(this, kValueOffset);
 }