Oilpan: Build fix after r178893

Source/core/animation/css/CSSAnimatableValueFactory.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 212 matching lines @@
     if (value)
         return AnimatableShapeValue::create(value);
     return AnimatableUnknown::create(CSSValueNone);
 }
 
 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));
 }
 
 static double fontWeightToDouble(FontWeight fontWeight)
 {
     switch (fontWeight) {
     case FontWeight100:
         return 100;
     case FontWeight200:
@@ skipping 262 matching lines @@
     case CSSPropertyZoom:
         return createFromDouble(style.zoom());
     default:
         ASSERT_NOT_REACHED();
         // This return value is to avoid a release crash if possible.
         return AnimatableUnknown::create(nullptr);
     }
 }
 
 } // namespace blink