[Oilpan]: Make StylePropertySet fully garbage collected.

Source/core/css/CSSCalculationValueTest.cpp

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 54 matching lines @@
 void initLengthArray(CSSLengthArray& lengthArray)
 {
     lengthArray.resize(CSSPrimitiveValue::LengthUnitTypeCount);
     for (size_t i = 0; i < CSSPrimitiveValue::LengthUnitTypeCount; ++i)
         lengthArray.at(i) = 0;
 }
 
 CSSLengthArray& setLengthArray(CSSLengthArray& lengthArray, String text)
 {
     initLengthArray(lengthArray);
-    RefPtr<MutableStylePropertySet> propertySet = MutableStylePropertySet::create();
+    RefPtrWillBeRawPtr<MutableStylePropertySet> propertySet = MutableStylePropertySet::create();
     propertySet->setProperty(CSSPropertyLeft, text);
     toCSSPrimitiveValue(propertySet->getPropertyCSSValue(CSSPropertyLeft).get())->accumulateLengthArray(lengthArray);
     return lengthArray;
 }
 
 bool lengthArraysEqual(CSSLengthArray& a, CSSLengthArray& b)
 {
     for (size_t i = 0; i < CSSPrimitiveValue::LengthUnitTypeCount; ++i) {
         if (a.at(i) != b.at(i))
             return false;
@@ skipping 103 matching lines @@
     expectation.at(CSSPrimitiveValue::UnitTypePercentage) = 10;
     EXPECT_TRUE(lengthArraysEqual(expectation, setLengthArray(actual, "calc(1in + 10%% - 6px)")));
 
     expectation.at(CSSPrimitiveValue::UnitTypePixels) = 15;
     expectation.at(CSSPrimitiveValue::UnitTypeFontSize) = 20;
     expectation.at(CSSPrimitiveValue::UnitTypePercentage) = -40;
     EXPECT_TRUE(lengthArraysEqual(expectation, setLengthArray(actual, "calc((1 * 2) * (5px + 20em / 2) - 80%% / (3 - 1) + 5px)")));
 }
 
 }