Issue 2401 - Fix checking of CSS rule type in order to be compatible with Firefox

chrome/content/cssProperties.js

 function splitSelector(selector)
 {
   if (selector.indexOf(",") == -1)
     return [selector];
 
   var selectors = [];
   var start = 0;
   var level = 0;
   var sep = "";
 
@@ skipping 47 matching lines @@
 
   findSelectors: function(stylesheet, selectors)
   {
     var rules = stylesheet.cssRules;
     if (!rules)
       return;
 
     for (var i = 0; i < rules.length; i++)
     {
       var rule = rules[i];
-      if (rule.type != this.window.CSSRule.STYLE_RULE)
+      if (rule.type != rule.STYLE_RULE)
         continue;
 
       var style = this.stringifyStyle(rule.style);
       for (var j = 0; j < this.patterns.length; j++)
       {
         var pattern = this.patterns[j];
         var regexp = pattern.regexp;
 
         if (typeof regexp == "string")
           regexp = pattern.regexp = new RegExp(regexp);
@@ skipping 41 matching lines @@
   apply: function()
   {
     if (this.patterns.length > 0)
     {
       var document = this.window.document;
       this.addSelectors(document.styleSheets);
       document.addEventListener("load", this.onLoad.bind(this), true);
     }
   }
 };