Move most of the [Pass]RefPtr's of CSSPrimitiveValue to our transition types.

Source/core/animation/AnimatableLength.h

Index: Source/core/animation/AnimatableLength.h
diff --git a/Source/core/animation/AnimatableLength.h b/Source/core/animation/AnimatableLength.h
index bf6433faa053c955649cd4ef5858b20ab18095b2..171d6c07d7215c063b631a2312a6b932dbb8e59e 100644
--- a/Source/core/animation/AnimatableLength.h
+++ b/Source/core/animation/AnimatableLength.h
@@ -114,7 +114,7 @@ private:
         return create(CSSCalcValue::createExpressionNode(leftAddend->toCSSCalcExpressionNode(), rightAddend->toCSSCalcExpressionNode(), CalcAdd));
     }
 
-    PassRefPtr<CSSPrimitiveValue> toCSSPrimitiveValue(NumberRange) const;
+    PassRefPtrWillBeRawPtr<CSSPrimitiveValue> toCSSPrimitiveValue(NumberRange) const;
     PassRefPtr<CSSCalcExpressionNode> toCSSCalcExpressionNode() const;
 
     PassRefPtr<AnimatableLength> scale(double) const;
@@ -155,7 +155,7 @@ private:
 
     RefPtr<CSSCalcExpressionNode> m_calcExpression;
 
-    mutable RefPtr<CSSPrimitiveValue> m_cachedCSSPrimitiveValue;
+    mutable RefPtrWillBePersistent<CSSPrimitiveValue> m_cachedCSSPrimitiveValue;
 
     friend class AnimationAnimatableLengthTest;
 };