Oilpan: Build fix after r178893

TBR=sof@chromium.org

Review URL: https://codereview.chromium.org/419743002

git-svn-id: svn://svn.chromium.org/blink/trunk@178899 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/animation/css/CSSAnimatableValueFactory.cpp

@@ -230,7 +230,7 @@ static double fontStretchToDouble(FontStretch fontStretch)
     return static_cast<unsigned>(fontStretch);
 }
 
-static PassRefPtr<AnimatableValue> createFromFontStretch(FontStretch fontStretch)
+static PassRefPtrWillBeRawPtr<AnimatableValue> createFromFontStretch(FontStretch fontStretch)
 {
     return createFromDouble(fontStretchToDouble(fontStretch));
 }