Move static field storage to end of Class instance

Change-Id: I90061999c9eef9d900e4269508b983a61f48b264
diff --git a/src/mark_sweep.h b/src/mark_sweep.h
index 47a703a..5f374ae 100644
--- a/src/mark_sweep.h
+++ b/src/mark_sweep.h
@@ -70,6 +70,9 @@
   // Grays references in static fields.
   void ScanStaticFields(const Class* klass);
 
+  // Used by ScanInstanceFields and ScanStaticFields
+  void ScanFields(const Object* obj, uint32_t ref_offsets, bool is_static);
+
   // Grays interface class objects.
   void ScanInterfaces(const Class* klass);