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

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 46f62f001d4f2da005586b16de92b8191520458a..e108248eb1d7118e75eec53fd88a6e5ac0a1a27b 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2768,8 +2768,14 @@ void Heap::CreateInitialObjects() {
   }
 
   {
+    Handle<WeakCell> cell = factory->NewWeakCell(factory->undefined_value());
+    cell->clear();
+    set_empty_weak_cell(*cell);
+
     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);