Support ignorance of base class finalizers.

tools/clang/blink_gc_plugin/tests/class_requires_finalization_mixin.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 "class_requires_finalization_mixin.h"
 
 namespace WebCore {
 
-void Mixin::trace(Visitor* visitor)
+void MixinFinalizable::trace(Visitor* visitor)
 {
     visitor->trace(m_onHeap);
 }
+
+void MixinNotFinalizable::trace(Visitor* visitor)
+{
+    visitor->trace(m_onHeap);
+}
 
 void NeedsFinalizer::trace(Visitor* visitor)
 {
     visitor->trace(m_obj);
-    Mixin::trace(visitor);
+    MixinFinalizable::trace(visitor);
 }
 
 void HasFinalizer::trace(Visitor* visitor)
 {
     visitor->trace(m_obj);
-    Mixin::trace(visitor);
+    MixinFinalizable::trace(visitor);
+}
+
+void NeedsNoFinalization::trace(Visitor* visitor)
+{
+    visitor->trace(m_obj);
+    MixinNotFinalizable::trace(visitor);
 }
 
 }