Make PropertyHandle instances const references where possible

third_party/WebKit/Source/core/animation/StringKeyframe.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef StringKeyframe_h
 #define StringKeyframe_h
 
 #include "core/animation/Keyframe.h"
 #include "core/css/StylePropertySet.h"
 
@@ skipping 139 matching lines @@
  private:
   StringKeyframe()
       : m_cssPropertyMap(MutableStylePropertySet::create(HTMLStandardMode)),
         m_presentationAttributeMap(
             MutableStylePropertySet::create(HTMLStandardMode)) {}
 
   StringKeyframe(const StringKeyframe& copyFrom);
 
   PassRefPtr<Keyframe> clone() const override;
   PassRefPtr<Keyframe::PropertySpecificKeyframe> createPropertySpecificKeyframe(
-      PropertyHandle) const override;
+      const PropertyHandle&) const override;
 
   bool isStringKeyframe() const override { return true; }
 
   Persistent<MutableStylePropertySet> m_cssPropertyMap;
   Persistent<MutableStylePropertySet> m_presentationAttributeMap;
   HashMap<const QualifiedName*, String> m_svgAttributeMap;
 };
 
 using CSSPropertySpecificKeyframe = StringKeyframe::CSSPropertySpecificKeyframe;
 using SVGPropertySpecificKeyframe = StringKeyframe::SVGPropertySpecificKeyframe;
@@ skipping 10 matching lines @@
                   value.isCSSPropertySpecificKeyframe());
 DEFINE_TYPE_CASTS(SVGPropertySpecificKeyframe,
                   Keyframe::PropertySpecificKeyframe,
                   value,
                   value->isSVGPropertySpecificKeyframe(),
                   value.isSVGPropertySpecificKeyframe());
 
 }  // namespace blink
 
 #endif