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

Source/core/css/CSSImageValue.h

Index: Source/core/css/CSSImageValue.h
diff --git a/Source/core/css/CSSImageValue.h b/Source/core/css/CSSImageValue.h
index 9019164dc9faad43d516699fbb17060e31a8ad31..87a4e375f513c6f7683e5d071c33c583e412eb41 100644
--- a/Source/core/css/CSSImageValue.h
+++ b/Source/core/css/CSSImageValue.h
@@ -66,6 +66,11 @@ public:
 
     bool knownToBeOpaque(const LayoutObject*) const;
 
+    PassRefPtrWillBeRawPtr<CSSImageValue> valueWithURLMadeAbsolute()
+    {
+        return create(KURL(ParsedURLString, m_absoluteURL), m_image.get());
+    }
+
     void setInitiator(const AtomicString& name) { m_initiatorName = name; }
 
     DECLARE_TRACE_AFTER_DISPATCH();