GC Plugin: test destructor access of part object.

tools/clang/blink_gc_plugin/tests/destructor_access_finalized_field.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "destructor_access_finalized_field.h"
 
 namespace blink {
 
 HeapObject::~HeapObject()
 {
     // Valid access to fields.
-    if (m_ref->foo() && !m_obj)
+    if (m_ref->foo() && !m_obj) {
         m_objs.size();
+        m_part.obj();
+    }
 
     // Invalid access to fields.
     bar(m_obj);
     m_obj->foo();
     m_objs[0];
 }
 
 void HeapObject::trace(Visitor* visitor)
 {
     visitor->trace(m_obj);
     visitor->trace(m_objs);
+    visitor->trace(m_part);
+}
+
+void PartOther::trace(Visitor* visitor)
+{
+    visitor->trace(m_obj);
 }
 
 }