- Account for live size in marker.

runtime/vm/gc_marker.cc

Index: runtime/vm/gc_marker.cc
===================================================================
--- runtime/vm/gc_marker.cc	(revision 35390)
+++ runtime/vm/gc_marker.cc	(working copy)
@@ -418,9 +418,10 @@
     RawObject* raw_obj = visitor->marking_stack()->Pop();
     visitor->VisitingOldObject(raw_obj);
     if (raw_obj->GetClassId() != kWeakPropertyCid) {
-      raw_obj->VisitPointers(visitor);
+      marked_bytes_ += raw_obj->VisitPointers(visitor);
     } else {
       RawWeakProperty* raw_weak = reinterpret_cast<RawWeakProperty*>(raw_obj);
+      marked_bytes_ += raw_weak->Size();
       ProcessWeakProperty(raw_weak, visitor);
     }
   }