Change first() and second() in CSSPairValue to return const references

Source/core/animation/DeferredLegacyStyleInterpolation.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 "config.h"
 #include "core/animation/DeferredLegacyStyleInterpolation.h"
 
 #include "core/animation/ElementAnimations.h"
 #include "core/animation/css/CSSAnimatableValueFactory.h"
 #include "core/css/CSSBasicShapes.h"
@@ skipping 112 matching lines @@
     size_t length = valueList.length();
     for (size_t index = 0; index < length; ++index) {
         if (interpolationRequiresStyleResolve(*valueList.item(index)))
             return true;
     }
     return false;
 }
 
 bool DeferredLegacyStyleInterpolation::interpolationRequiresStyleResolve(const CSSValuePair& pair)
 {
-    return interpolationRequiresStyleResolve(*pair.first())
-        || interpolationRequiresStyleResolve(*pair.second());
+    return interpolationRequiresStyleResolve(pair.first())
+        || interpolationRequiresStyleResolve(pair.second());
 }
 
 bool DeferredLegacyStyleInterpolation::interpolationRequiresStyleResolve(const CSSBasicShape& shape)
 {
     // FIXME: Should determine the specific shape, and inspect the members.
     return false;
 }
 
 bool DeferredLegacyStyleInterpolation::interpolationRequiresStyleResolve(const CSSQuadValue& quad)
 {
     return interpolationRequiresStyleResolve(*quad.top())
         || interpolationRequiresStyleResolve(*quad.right())
         || interpolationRequiresStyleResolve(*quad.bottom())
         || interpolationRequiresStyleResolve(*quad.left());
 }
 
 DEFINE_TRACE(DeferredLegacyStyleInterpolation)
 {
     visitor->trace(m_startCSSValue);
     visitor->trace(m_endCSSValue);
     visitor->trace(m_innerInterpolation);
     StyleInterpolation::trace(visitor);
 }
 
 }