BackgroundImage incorrectly returns empty url() when created on-the-fly

Source/core/style/StyleGeneratedImage.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 24 matching lines @@
 class CORE_EXPORT StyleGeneratedImage final : public StyleImage {
 public:
     static PassRefPtrWillBeRawPtr<StyleGeneratedImage> create(CSSImageGeneratorValue* value)
     {
         return adoptRefWillBeNoop(new StyleGeneratedImage(value));
     }
 
     WrappedImagePtr data() const override { return m_imageGeneratorValue.get(); }
 
     PassRefPtrWillBeRawPtr<CSSValue> cssValue() const override;
+    PassRefPtrWillBeRawPtr<CSSValue> computedCSSValue() const override;
 
     LayoutSize imageSize(const LayoutObject*, float multiplier) const override;
     bool imageHasRelativeWidth() const override { return !m_fixedSize; }
     bool imageHasRelativeHeight() const override { return !m_fixedSize; }
     void computeIntrinsicDimensions(const LayoutObject*, Length& intrinsicWidth, Length& intrinsicHeight, FloatSize& intrinsicRatio) override;
     bool usesImageContainerSize() const override { return !m_fixedSize; }
     void setContainerSizeForLayoutObject(const LayoutObject*, const IntSize& containerSize, float) override { m_containerSize = containerSize; }
     void addClient(LayoutObject*) override;
     void removeClient(LayoutObject*) override;
     PassRefPtr<Image> image(LayoutObject*, const IntSize&) const override;
     bool knownToBeOpaque(const LayoutObject*) const override;
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     StyleGeneratedImage(PassRefPtrWillBeRawPtr<CSSImageGeneratorValue>);
 
     RefPtrWillBeMember<CSSImageGeneratorValue> m_imageGeneratorValue;
     IntSize m_containerSize;
     bool m_fixedSize;
 };
 
 }
 #endif