make the microsummary service support <link> tags with rel=space-separated list of words and ignore case of "microsummary" rel value

Patch by Justin Dolske.
bug=342228
r=myk

browser/components/microsummaries/src/nsMicrosummaryService.js.in

@@ -1414,9 +1414,18 @@ MicrosummarySet.prototype = {
     for ( var i = 0; i < links.length; i++ ) {
       var link = links[i];
 
-      if (link.getAttribute("rel") != "microsummary")
+      if(!link.hasAttribute("rel"))
         continue;
 
+      var relAttr = link.getAttribute("rel");
+
+      // The attribute's value can be a space-separated list of link types,
+      // check to see if "microsummary" is one of them.
+      var linkTypes = relAttr.split(/\s+/);
+      if (!linkTypes.some( function(v) { return v.toLowerCase() == "microsummary"; }))
+        continue;
+
+
       // Unlike the "href" attribute, the "href" property contains
       // an absolute URI spec, so we use it here to create the URI.
       var generatorURI = this._ios.newURI(link.href,