[heap] Move slot recording of weak fields in native context to native context list retainer.

BUG=

Review URL: https://codereview.chromium.org/1463483002

Cr-Commit-Position: refs/heads/master@{#32109}

src/heap/objects-visiting-inl.h

@@ -304,13 +304,6 @@ void StaticMarkingVisitor<StaticVisitor>::VisitNativeContext(
     Map* map, HeapObject* object) {
   FixedBodyVisitor<StaticVisitor, Context::MarkCompactBodyDescriptor,
                    void>::Visit(map, object);
-
-  MarkCompactCollector* collector = map->GetHeap()->mark_compact_collector();
-  for (int idx = Context::FIRST_WEAK_SLOT; idx < Context::NATIVE_CONTEXT_SLOTS;
-       ++idx) {
-    Object** slot = Context::cast(object)->RawFieldOfElementAt(idx);
-    collector->RecordSlot(object, slot, *slot);
-  }
 }
 
 

src/heap/objects-visiting.cc

@@ -307,9 +307,17 @@ struct WeakListVisitor<Context> {
     DoWeakList<JSFunction>(heap, context, retainer,
                            Context::OPTIMIZED_FUNCTIONS_LIST);
 
-    // Code objects are always allocated in Code space, we do not have to visit
-    // them during scavenges.
     if (heap->gc_state() == Heap::MARK_COMPACT) {
+      // Record the slots of the weak entries in the native context.
+      MarkCompactCollector* collector = heap->mark_compact_collector();
+      for (int idx = Context::FIRST_WEAK_SLOT;
+           idx < Context::NATIVE_CONTEXT_SLOTS; ++idx) {
+        Object** slot = Context::cast(context)->RawFieldOfElementAt(idx);
+        collector->RecordSlot(context, slot, *slot);
+      }
+      // Code objects are always allocated in Code space, we do not have to
+      // visit
+      // them during scavenges.
       DoWeakList<Code>(heap, context, retainer, Context::OPTIMIZED_CODE_LIST);
       DoWeakList<Code>(heap, context, retainer, Context::DEOPTIMIZED_CODE_LIST);
     }