Add description for CSSURLImageValue constructor. (w3c#440)

nainar · shans · commit cdc9a4af81f4 · 2017-08-04T14:55:50.000+10:00
diff --git a/css-typed-om/Overview.bs b/css-typed-om/Overview.bs
@@ -2220,6 +2220,19 @@ Issue: Does the loading lifecycle need to be described here?
 {{CSSURLImageValue}} objects represent {{CSSImageValue}}s that match the <<url>> production. For these
 objects, the {{CSSURLImageValue/url}} attribute contains the URL that references the image.
 
+<div algorithm>
+    The <dfn constructor for=CSSURLImageValue>CSSURLImageValue(|url|)</dfn> constructor must,
+    when called,
+    perform the following steps:
+
+    1. If the |url| passed into the constructor doesn't correctly 
+        parse as a <<url>>, throw a {{TypeError}} and exit this algorithm.
+    2. Else, return a new {{CSSURLImageValue}}
+        with its {{CSSURLImageValue/url}} internal slot
+        set to |url|.
+</div>
+
+
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