Make maps in monomorphic IC stubs weak.

src/objects-visiting-inl.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 294 matching lines @@
 void StaticMarkingVisitor<StaticVisitor>::VisitCodeTarget(
     Heap* heap, RelocInfo* rinfo) {
   ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode()));
   Code* target = Code::GetCodeFromTargetAddress(rinfo->target_address());
   // Monomorphic ICs are preserved when possible, but need to be flushed
   // when they might be keeping a Context alive, or when the heap is about
   // to be serialized.
   if (FLAG_cleanup_code_caches_at_gc && target->is_inline_cache_stub()
       && (target->ic_state() == MEGAMORPHIC || target->ic_state() == GENERIC ||
           target->ic_state() == POLYMORPHIC || heap->flush_monomorphic_ics() ||
-          Serializer::enabled() || target->ic_age() != heap->global_ic_age())) {
+          Serializer::enabled() || target->ic_age() != heap->global_ic_age() ||
+          target->is_invalidated_weak_stub())) {
     IC::Clear(target->GetIsolate(), rinfo->pc(),
               rinfo->host()->constant_pool());
     target = Code::GetCodeFromTargetAddress(rinfo->target_address());
   }
   heap->mark_compact_collector()->RecordRelocSlot(rinfo, target);
   StaticVisitor::MarkObject(heap, target);
 }
 
 
 template<typename StaticVisitor>
@@ skipping 619 matching lines @@
   RelocIterator it(this, mode_mask);
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>(heap);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_INL_H_