- Implement a simple old-generation marker.

vm/vm_sources.gypi

 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This file contains all sources (vm and tests) for the dart virtual machine.
 # Unit test files need to have a '_test' suffix appended to the name.
 {
   'sources': [
     'allocation.cc',
     'allocation.h',
@@ skipping 81 matching lines @@
     'debuginfo.h',
     'debuginfo_linux.cc',
     'debuginfo_macos.cc',
     'debuginfo_win.cc',
     'exceptions.cc',
     'exceptions.h',
     'exceptions_test.cc',
     'flags.cc',
     'flags.h',
     'flags_test.cc',
+    'gc_marker.cc',
+    'gc_marker.h',
     'gdbjit_linux.cc',
     'gdbjit_linux.h',
     'globals.h',
     'growable_array.h',
     'growable_array_test.cc',
     'handles.cc',
     'handles.h',
     'handles_impl.h',
     'handles_test.cc',
     'heap.cc',
@@ skipping 130 matching lines @@
     'virtual_memory_test.cc',
     'virtual_memory_win.cc',
     'verifier.cc',
     'verifier.h',
     'visitor.h',
     'zone.cc',
     'zone.h',
     'zone_test.cc',
   ],
 }