Make PropertyHandle instances const references where possible

third_party/WebKit/Source/core/animation/Keyframe.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 Keyframe_h
 #define Keyframe_h
 
 #include "core/CoreExport.h"
 #include "core/animation/AnimationEffectReadOnly.h"
 #include "core/animation/EffectModel.h"
@@ skipping 80 matching lines @@
     virtual bool isAnimatableValuePropertySpecificKeyframe() const {
       return false;
     }
     virtual bool isCSSPropertySpecificKeyframe() const { return false; }
     virtual bool isSVGPropertySpecificKeyframe() const { return false; }
 
     virtual PassRefPtr<PropertySpecificKeyframe> neutralKeyframe(
         double offset,
         PassRefPtr<TimingFunction> easing) const = 0;
     virtual PassRefPtr<Interpolation> createInterpolation(
-        PropertyHandle,
+        const PropertyHandle&,
         const Keyframe::PropertySpecificKeyframe& end) const;
 
    protected:
     PropertySpecificKeyframe(double offset,
                              PassRefPtr<TimingFunction> easing,
                              EffectModel::CompositeOperation);
 
     double m_offset;
     RefPtr<TimingFunction> m_easing;
     EffectModel::CompositeOperation m_composite;
   };
 
   virtual PassRefPtr<PropertySpecificKeyframe> createPropertySpecificKeyframe(
-      PropertyHandle) const = 0;
+      const PropertyHandle&) const = 0;
 
  protected:
   Keyframe()
       : m_offset(nullValue()),
         m_composite(EffectModel::CompositeReplace),
         m_easing(LinearTimingFunction::shared()) {}
   Keyframe(double offset,
            EffectModel::CompositeOperation composite,
            PassRefPtr<TimingFunction> easing)
       : m_offset(offset), m_composite(composite), m_easing(easing) {}
 
   double m_offset;
   EffectModel::CompositeOperation m_composite;
   RefPtr<TimingFunction> m_easing;
 };
 
 using PropertySpecificKeyframe = Keyframe::PropertySpecificKeyframe;
 
 }  // namespace blink
 
 #endif  // Keyframe_h