Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/animation/DocumentTimelineTest.cpp

Index: Source/core/animation/DocumentTimelineTest.cpp
diff --git a/Source/core/animation/DocumentTimelineTest.cpp b/Source/core/animation/DocumentTimelineTest.cpp
index 4dd27f5f69bf5ceb5cb2a0eba7766999bd264500..f2c53ad5105f9cb7d4dcd6b768d8bf110b6b40de 100644
--- a/Source/core/animation/DocumentTimelineTest.cpp
+++ b/Source/core/animation/DocumentTimelineTest.cpp
@@ -252,7 +252,7 @@ TEST_F(AnimationDocumentTimelineTest, DelayBeforeAnimationStart)
     timing.iterationDuration = 2;
     timing.startDelay = 5;
 
-    RefPtr<Animation> anim = Animation::create(element.get(), 0, timing);
+    RefPtr<Animation> anim = Animation::create(element.get(), nullptr, timing);
 
     timeline->play(anim.get());
 
@@ -276,10 +276,10 @@ TEST_F(AnimationDocumentTimelineTest, PlayAfterDocumentDeref)
     timing.startDelay = 5;
 
     timeline = document->timeline();
-    element = 0;
-    document = 0;
+    element = nullptr;
+    document = nullptr;
 
-    RefPtr<Animation> anim = Animation::create(0, 0, timing);
+    RefPtr<Animation> anim = Animation::create(nullptr, nullptr, timing);
     // Test passes if this does not crash.
     timeline->play(anim.get());
 }