Use <string> serialization rules for computed value of reference filter

third_party/WebKit/Source/core/css/ComputedStyleCSSValueMapping.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ skipping 1195 matching lines @@
 
     RefPtrWillBeRawPtr<CSSValueList> list = CSSValueList::createSpaceSeparated();
 
     RefPtrWillBeRawPtr<CSSFunctionValue> filterValue = nullptr;
 
     for (const auto& operation : filterOperations.operations()) {
         FilterOperation* filterOperation = operation.get();
         switch (filterOperation->type()) {
         case FilterOperation::REFERENCE:
             filterValue = CSSFunctionValue::create(CSSValueUrl);
-            filterValue->append(CSSCustomIdentValue::create(toReferenceFilterOperation(filterOperation)->url()));
+            filterValue->append(CSSStringValue::create(toReferenceFilterOperation(filterOperation)->url()));
             break;
         case FilterOperation::GRAYSCALE:
             filterValue = CSSFunctionValue::create(CSSValueGrayscale);
             filterValue->append(cssValuePool().createValue(toBasicColorMatrixFilterOperation(filterOperation)->amount(), CSSPrimitiveValue::UnitType::Number));
             break;
         case FilterOperation::SEPIA:
             filterValue = CSSFunctionValue::create(CSSValueSepia);
             filterValue->append(cssValuePool().createValue(toBasicColorMatrixFilterOperation(filterOperation)->amount(), CSSPrimitiveValue::UnitType::Number));
             break;
         case FilterOperation::SATURATE:
@@ skipping 1524 matching lines @@
     case CSSPropertyAll:
         return nullptr;
     default:
         break;
     }
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 
 } // namespace blink