Change CSSImageValue's member variables from String to AtomicString

Source/core/css/parser/CSSPropertyParser.cpp

Index: Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/Source/core/css/parser/CSSPropertyParser.cpp b/Source/core/css/parser/CSSPropertyParser.cpp
index 4ddccd5395483aec08c2bc01bb68c7d3250e60ba..0554cf6e27d5a60eed966b9df10aca0e53d7df95 100644
--- a/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/Source/core/css/parser/CSSPropertyParser.cpp
@@ -314,7 +314,7 @@ inline PassRefPtrWillBeRawPtr<CSSPrimitiveValue> CSSPropertyParser::createPrimit
     return cssValuePool().createValue(value->string, CSSPrimitiveValue::UnitType::CustomIdentifier);
 }
 
-inline PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::createCSSImageValueWithReferrer(const String& rawValue, const KURL& url)
+inline PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::createCSSImageValueWithReferrer(const AtomicString& rawValue, const KURL& url)
 {
     RefPtrWillBeRawPtr<CSSValue> imageValue = CSSImageValue::create(rawValue, url);
     toCSSImageValue(imageValue.get())->setReferrer(m_context.referrer());
@@ -593,7 +593,7 @@ bool CSSPropertyParser::parseValue(CSSPropertyID unresolvedProperty, bool import
             if (value->unit() == CSSPrimitiveValue::UnitType::URI) {
                 String uri = value->string;

[Timothy Loh, 2015/09/18 01:52:30]

I think this line does a conversion, might as well make it convert to
AtomicString directly.

[hajimehoshi, 2015/09/18 04:23:08]

Done.

                 if (!uri.isNull())
-                    image = createCSSImageValueWithReferrer(uri, completeURL(uri));
+                    image = createCSSImageValueWithReferrer(AtomicString(uri), completeURL(uri));
             } else if (value->m_unit == CSSParserValue::Function && value->function->id == CSSValueWebkitImageSet) {
                 image = parseImageSet(m_valueList);
                 if (!image)