[heap] Use specialized IterateBodyFast in evacuator and scavenger.

Currently they are using a generic IterateBody(ObjectVisit*), which has
an overhead of virtual table lookup for each visited pointer.

Change-Id: I97268bf7fe63f8c99834d5fc31b4ce18a0fa5655
Reviewed-on: https://chromium-review.googlesource.com/979437
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52220}

src/heap/mark-compact.cc

@@ -1686,7 +1686,7 @@ class EvacuateRecordOnlyVisitor final : public HeapObjectVisitor {
 
   inline bool Visit(HeapObject* object, int size) {
     RecordMigratedSlotVisitor visitor(heap_->mark_compact_collector());
-    object->IterateBody(&visitor);
+    object->IterateBodyFast(&visitor);
     return true;
   }
 
@@ -3715,7 +3715,7 @@ class ToSpaceUpdatingItem : public UpdatingItem {
       HeapObject* object = HeapObject::FromAddress(cur);
       Map* map = object->map();
       int size = object->SizeFromMap(map);
-      object->IterateBody(map, size, &visitor);
+      object->IterateBodyFast(map, size, &visitor);
       cur += size;
     }
   }

src/heap/scavenger.cc

@@ -103,7 +103,7 @@ void Scavenger::IterateAndScavengePromotedObject(HeapObject* target, int size) {
       is_compacting_ &&
       heap()->incremental_marking()->atomic_marking_state()->IsBlack(target);
   IterateAndScavengePromotedObjectsVisitor visitor(heap(), this, record_slots);
-  target->IterateBody(target->map(), size, &visitor);
+  target->IterateBodyFast(target->map(), size, &visitor);
 }
 
 void Scavenger::AddPageToSweeperIfNecessary(MemoryChunk* page) {