Do not zero-initialize RawPtr.

Source/core/animation/CompositorAnimationsTest.cpp

Index: Source/core/animation/CompositorAnimationsTest.cpp
diff --git a/Source/core/animation/CompositorAnimationsTest.cpp b/Source/core/animation/CompositorAnimationsTest.cpp
index 2bd811994e1969fd1b901cf8795b5821840ff4b4..824b187ab0a4594385290869c2808939491cbd51 100644
--- a/Source/core/animation/CompositorAnimationsTest.cpp
+++ b/Source/core/animation/CompositorAnimationsTest.cpp
@@ -150,7 +150,7 @@ public:
 
     PassRefPtrWillBeRawPtr<Keyframe> createDefaultKeyframe(CSSPropertyID id, AnimationEffect::CompositeOperation op, double offset = 0)
     {
-        RefPtrWillBeRawPtr<AnimatableValue> value;
+        RefPtrWillBeRawPtr<AnimatableValue> value = nullptr;
         if (id == CSSPropertyWebkitTransform)
             value = AnimatableTransform::create(TransformOperations());
         else
@@ -207,7 +207,7 @@ public:
         if (!HasFatalFailure()) {
             return KeyframeEffectModel::create(frames);
         }
-        return PassRefPtrWillBeRawPtr<KeyframeEffectModel>();
+        return nullptr;
     }
 
 };