Make PropertyHandle instances const references where possible

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

 // 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.
 
 #include "core/animation/StringKeyframe.h"
 
 #include "core/StylePropertyShorthand.h"
 #include "core/animation/css/CSSAnimations.h"
 #include "core/css/CSSCustomPropertyDeclaration.h"
 #include "core/css/CSSPropertyMetadata.h"
@@ skipping 82 matching lines @@
     properties.add(PropertyHandle(*key));
 
   return properties;
 }
 
 PassRefPtr<Keyframe> StringKeyframe::clone() const {
   return adoptRef(new StringKeyframe(*this));
 }
 
 PassRefPtr<Keyframe::PropertySpecificKeyframe>
-StringKeyframe::createPropertySpecificKeyframe(PropertyHandle property) const {
+StringKeyframe::createPropertySpecificKeyframe(
+    const PropertyHandle& property) const {
   if (property.isCSSProperty())
     return CSSPropertySpecificKeyframe::create(
         offset(), &easing(), &cssPropertyValue(property), composite());
 
   if (property.isPresentationAttribute())
     return CSSPropertySpecificKeyframe::create(
         offset(), &easing(),
         &presentationAttributeValue(property.presentationAttribute()),
         composite());
 
@@ skipping 35 matching lines @@
 }
 
 PassRefPtr<Keyframe::PropertySpecificKeyframe>
 SVGPropertySpecificKeyframe::neutralKeyframe(
     double offset,
     PassRefPtr<TimingFunction> easing) const {
   return create(offset, std::move(easing), String(), EffectModel::CompositeAdd);
 }
 
 }  // namespace blink