Allow race-full access of map instance size when sweeping concurrently.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index ae24cd6b45b6166b6262137d7d7473f28a81e330..b43a6ec33dac6ce59ce3cdbcd8f546bd4daeba8d 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -10224,12 +10224,7 @@ static void GetMinInobjectSlack(Map* map, void* data) {
 
 static void ShrinkInstanceSize(Map* map, void* data) {
   int slack = *reinterpret_cast<int*>(data);
-  map->set_inobject_properties(map->inobject_properties() - slack);
-  map->set_unused_property_fields(map->unused_property_fields() - slack);
-  map->set_instance_size(map->instance_size() - slack * kPointerSize);
-
-  // Visitor id might depend on the instance size, recalculate it.
-  map->set_visitor_id(StaticVisitorBase::GetVisitorId(map));
+  map->Shrink(slack);

[Michael Starzinger, 2014/04/08 11:34:22]

nit: Can we call that Map::ShrinkInstanceSize for readability?

 }