Use WeakCells in the optimized code map rather than traversing in pause.

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/scopeinfo.h"
 #include "src/base/bits.h"
@@ skipping 2759 matching lines @@
     Object* megamorphic = *TypeFeedbackVector::MegamorphicSentinel(isolate());
     dummy_vector->Set(load_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
     dummy_vector->Set(keyed_load_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
     dummy_vector->Set(store_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
     dummy_vector->Set(keyed_store_ic_slot, megamorphic, SKIP_WRITE_BARRIER);
 
     set_dummy_vector(*dummy_vector);
   }
 
   {
+    Handle<WeakCell> cell = factory->NewWeakCell(factory->undefined_value());
+    set_empty_weak_cell(*cell);
+    cell->clear();
+
     Handle<FixedArray> cleared_optimized_code_map =
         factory->NewFixedArray(SharedFunctionInfo::kEntriesStart, TENURED);
+    cleared_optimized_code_map->set(SharedFunctionInfo::kSharedCodeIndex,
+                                    *cell);
     STATIC_ASSERT(SharedFunctionInfo::kEntriesStart == 1 &&
                   SharedFunctionInfo::kSharedCodeIndex == 0);
     set_cleared_optimized_code_map(*cleared_optimized_code_map);
   }
 
   set_detached_contexts(empty_fixed_array());
   set_retained_maps(ArrayList::cast(empty_fixed_array()));
 
   set_weak_object_to_code_table(
       *WeakHashTable::New(isolate(), 16, USE_DEFAULT_MINIMUM_CAPACITY,
@@ skipping 3325 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8