Object's body descriptors refactoring.

src/heap/scavenger.cc

Index: src/heap/scavenger.cc
diff --git a/src/heap/scavenger.cc b/src/heap/scavenger.cc
index 31f1ee55b73dcdbc57007881dfa63d951669c4c7..e2ac8d4ffdfbed886b66dc568fa8fc0c87a63efa 100644
--- a/src/heap/scavenger.cc
+++ b/src/heap/scavenger.cc
@@ -266,7 +266,8 @@ class ScavengingVisitor : public StaticVisitorBase {
 
   static inline void EvacuateFixedArray(Map* map, HeapObject** slot,
                                         HeapObject* object) {
-    int object_size = FixedArray::BodyDescriptor::SizeOf(map, object);
+    int length = reinterpret_cast<FixedArray*>(object)->synchronized_length();
+    int object_size = FixedArray::SizeFor(length);
     EvacuateObject<POINTER_OBJECT, kWordAligned>(map, slot, object,
                                                  object_size);
   }