Make <attr-name> accept any CSS identifier

third_party/WebKit/LayoutTests/fast/css/attr-parsing.html

 <style>
 #a { content: attr(b); }
 #c { content: attr("x"); }
 #d { content: attr(0); }
 #e { content: attr(0.0); }
 #f { content: attr(0%); }
 #g { content: attr(0px); }
 #h { content: attr(); }
 #i { content: attr(+0); }
 #j { content: attr(-k); }
@@ skipping 15 matching lines @@
 <p>Expected result:</p>
 
 <pre id="expected">#a { content: attr(b); }
 #c { }
 #d { }
 #e { }
 #f { }
 #g { }
 #h { }
 #i { }
-#j { }
+#j { content: attr(-k); }
 #l { }
 #n { }
 #q { }
 #r { }
 #s { }
 #t { }
 #u { }
 </pre>
 
 <script>
 
 if (window.testRunner)
     testRunner.dumpAsText();
 
 var rules = document.styleSheets[0].cssRules;
 var text = "";
 for (var i = 0; i < rules.length; i++) {
     text += rules.item(i).cssText;
     text += "\n";
 }
 
 document.getElementById("result").appendChild(document.createTextNode(text));
 
 if (document.getElementById("result").firstChild.data === document.getElementById("expected").firstChild.data)
     document.getElementById("message").firstChild.data = "SUCCESS";
 else
     document.getElementById("message").firstChild.data = "FAILURE";
 
 </script>