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 976130218f98a741c4beaa9fc2078d74f32cef1c..a5a4675650f0ddc2568d1b21e2d6a5f8bc1599e5 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -2777,8 +2777,14 @@ void Heap::CreateInitialObjects() {
   }
 
   {
+    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);