Parallelize marking phase of mark-sweep/compact collection cycle.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index e284454c8eba5b13160560e892e3e98d1cd10cca..14f37f8217e7b2996328775b2a4fe9f16860b1af 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1043,7 +1043,11 @@ class HeapObject: public Object {
   inline bool IsMarked();
 
   // Mutate this object's map pointer to indicate that the object is live.
-  inline void SetMark();
+  inline bool SetMark();
+
+  // Mutate this object's map pointer to indicate that the object is live.
+  inline bool SetMarkExclusively();
+
 
   // Mutate this object's map pointer to remove the indication that the
   // object is live (ie, partially restore the map pointer).
@@ -3009,6 +3013,9 @@ class Code: public HeapObject {
 
   template<typename StaticVisitor>
   inline void CodeIterateBody();
+
+  template<typename StaticVisitor, typename Data>
+  inline void CodeIterateBody(Data data);
 #ifdef DEBUG
   void CodePrint();
   void CodeVerify();