Generalize virtually dispatched scavenger to virtually dispatched specialized visitors.

src/mark-compact.h

Index: src/mark-compact.h
diff --git a/src/mark-compact.h b/src/mark-compact.h
index 1d289a75928aefa8fba0c6b2914e03a4769bd376..ad635867c396dbe0759de49138deeeb779ff2ada 100644
--- a/src/mark-compact.h
+++ b/src/mark-compact.h
@@ -86,6 +86,9 @@ class MarkCompactCollector: public AllStatic {
     force_compaction_ = value;
   }
 
+
+  static void Initialize();
+
   // Prepares for GC by resetting relocation info in old and map spaces and
   // choosing spaces to compact.
   static void Prepare(GCTracer* tracer);
@@ -171,6 +174,7 @@ class MarkCompactCollector: public AllStatic {
 
   friend class RootMarkingVisitor;
   friend class MarkingVisitor;
+  friend class StaticMarkingVisitor;
 
   // Marking operations for objects reachable from roots.
   static void MarkLiveObjects();
@@ -214,17 +218,17 @@ class MarkCompactCollector: public AllStatic {
   // Mark all objects in an object group with at least one marked
   // object, then all objects reachable from marked objects in object
   // groups, and repeat.
-  static void ProcessObjectGroups(MarkingVisitor* visitor);
+  static void ProcessObjectGroups();
 
   // Mark objects reachable (transitively) from objects in the marking stack
   // or overflowed in the heap.
-  static void ProcessMarkingStack(MarkingVisitor* visitor);
+  static void ProcessMarkingStack();
 
   // Mark objects reachable (transitively) from objects in the marking
   // stack.  This function empties the marking stack, but may leave
   // overflowed objects in the heap, in which case the marking stack's
   // overflow flag will be set.
-  static void EmptyMarkingStack(MarkingVisitor* visitor);
+  static void EmptyMarkingStack();
 
   // Refill the marking stack with overflowed objects from the heap.  This
   // function either leaves the marking stack full or clears the overflow