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

src/heap/objects-visiting.h

 // 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.
 
 #ifndef V8_OBJECTS_VISITING_H_
 #define V8_OBJECTS_VISITING_H_
 
 #include "src/allocation.h"
 #include "src/heap/heap.h"
 #include "src/heap/spaces.h"
@@ skipping 365 matching lines @@
   INLINE(static void VisitJSTypedArray(Map* map, HeapObject* object));
   INLINE(static void VisitJSDataView(Map* map, HeapObject* object));
   INLINE(static void VisitNativeContext(Map* map, HeapObject* object));
   INLINE(static void VisitBytecodeArray(Map* map, HeapObject* object));
 
   // Mark pointers in a Map and its TransitionArray together, possibly
   // treating transitions or back pointers weak.
   static void MarkMapContents(Heap* heap, Map* map);
   static void MarkTransitionArray(Heap* heap, TransitionArray* transitions);
 
-  // Mark pointers in the optimized code map that should act as strong
-  // references, possibly treating some entries weak.
-  static void MarkOptimizedCodeMap(Heap* heap, FixedArray* code_map);
-
   // Mark non-optimized code for functions inlined into the given optimized
   // code. This will prevent it from being flushed.
   static void MarkInlinedFunctionsCode(Heap* heap, Code* code);
 
   // Code flushing support.
   INLINE(static bool IsFlushable(Heap* heap, JSFunction* function));
   INLINE(static bool IsFlushable(Heap* heap, SharedFunctionInfo* shared_info));
 
   // Helpers used by code flushing support that visit pointer fields and treat
   // references to code objects either strongly or weakly.
@@ skipping 37 matching lines @@
 // 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);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_VISITING_H_