Make maps in monomorphic IC stubs weak.

src/objects-visiting.h

 // 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 465 matching lines @@
 
   static VisitorDispatchTable<Callback> table_;
 };
 
 
 template<typename StaticVisitor>
 VisitorDispatchTable<typename StaticMarkingVisitor<StaticVisitor>::Callback>
     StaticMarkingVisitor<StaticVisitor>::table_;
 
 
+class WeakObjectRetainer;
+
+
+// A weak list is single linked list where each element has a weak pointer to
+// the next element. Given the head of the list, this function removes dead
+// elements from the list and if requested records slots for next-element
+// pointers. The template parameter T is a WeakListVisitor that defines how to
+// access the next-element pointers.
+template <class T>
+Object* VisitWeakList(Heap* heap,
+                      Object* list,
+                      WeakObjectRetainer* retainer,
+                      bool record_slots);
+
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_H_