Oilpan: fix webkit unit tests after r191696 (d325d00a5).

Source/core/animation/LengthStyleInterpolation.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/LengthStyleInterpolation.h"
 
 #include "core/animation/css/CSSAnimatableValueFactory.h"
 #include "core/css/CSSCalculationValue.h"
 #include "core/css/resolver/StyleBuilder.h"
@@ skipping 189 matching lines @@
 
 static CSSPrimitiveValue::UnitType toUnitType(int lengthUnitType)
 {
     return static_cast<CSSPrimitiveValue::UnitType>(CSSPrimitiveValue::lengthUnitTypeToUnitType(static_cast<CSSPrimitiveValue::LengthUnitType>(lengthUnitType)));
 }
 
 static PassRefPtrWillBeRawPtr<CSSCalcExpressionNode> constructCalcExpression(const InterpolableList* list)
 {
     const InterpolableList* listOfValues = toInterpolableList(list->get(0));
     const InterpolableList* listOfTypes = toInterpolableList(list->get(1));
-    RefPtrWillBeRawPtr<CSSCalcExpressionNode> expression;
+    RefPtrWillBeRawPtr<CSSCalcExpressionNode> expression = nullptr;
     for (size_t position = 0; position < CSSPrimitiveValue::LengthUnitTypeCount; position++) {
         const InterpolableNumber *subValueType = toInterpolableNumber(listOfTypes->get(position));
         if (!subValueType->value())
             continue;
         double value = toInterpolableNumber(listOfValues->get(position))->value();
         RefPtrWillBeRawPtr<CSSCalcExpressionNode> currentTerm = CSSCalcValue::createExpressionNode(CSSPrimitiveValue::create(value, toUnitType(position)));
         if (expression)
             expression = CSSCalcValue::createExpressionNode(expression.release(), currentTerm.release(), CalcAdd);
         else
             expression = currentTerm.release();
@@ skipping 80 matching lines @@
         StyleBuilder::applyProperty(m_id, state, fromInterpolableValue(*m_cachedValue, m_range).get());
     }
 }
 
 DEFINE_TRACE(LengthStyleInterpolation)
 {
     StyleInterpolation::trace(visitor);
 }
 
 }