[oilpan]: Avoid refcounting QualifiedName's nullQName when tracing.

Source/core/animation/AnimationTimelineTest.cpp

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 72 matching lines @@
         AnimationTimeline::PlatformTiming::trace(visitor);
     }
 };
 
 class AnimationAnimationTimelineTest : public ::testing::Test {
 protected:
     virtual void SetUp()
     {
         document = Document::create();
         document->animationClock().resetTimeForTesting();
-        element = Element::create(nullQName() , document.get());
+        element = Element::create(QualifiedName::null() , document.get());
         platformTiming = new MockPlatformTiming;
         timeline = AnimationTimeline::create(document.get(), adoptPtrWillBeNoop(platformTiming));
         ASSERT_EQ(0, timeline->currentTimeInternal());
     }
 
     virtual void TearDown()
     {
         document.release();
         element.release();
         timeline.release();
@@ skipping 180 matching lines @@
 
 TEST_F(AnimationAnimationTimelineTest, UseAnimationPlayerAfterTimelineDeref)
 {
     RefPtrWillBeRawPtr<AnimationPlayer> player = timeline->createAnimationPlayer(0);
     timeline.clear();
     // Test passes if this does not crash.
     player->setStartTime(0);
 }
 
 }