Introduce one way dependencies into object grouping.

src/mark-compact.h

 // Copyright 2006-2008 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 202 matching lines @@
   static void MarkRoots(RootMarkingVisitor* visitor);
 
   // Mark the symbol table specially.  References to symbols from the
   // symbol table are weak.
   static void MarkSymbolTable();
 
   // Mark objects in object groups that have at least one object in the
   // group marked.
   static void MarkObjectGroups();
 
-  // 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();
+  // Mark objects in implicit references groups if their parent object
+  // is marked.
+  static void MarkImplicitRefGroups();
+
+  // Mark all objects which are reachable due to host application
+  // logic like object groups or implicit references' groups.
+  static void ProcessExternalMarking();
 
   // Mark objects reachable (transitively) from objects in the marking stack
   // or overflowed in the heap.
   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();
@@ skipping 187 matching lines @@
 
   friend class UnmarkObjectVisitor;
   static void UnmarkObject(HeapObject* obj);
 #endif
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_