DevTools: CssChecker: avoid selector crafting in AuditsPanel.

Source/devtools/front_end/audits/AuditResultView.js

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 85 matching lines @@
 
         if (typeof result.value === "string") {
             title = result.value;
             if (result.violationCount)
                 title = String.sprintf("%s (%d)", title, result.violationCount);
         }
 
         var titleFragment = createDocumentFragment();
         if (severity) {
             var severityElement = createElement("div");
-            severityElement.className = "severity-" + severity;
+            severityElement.classList.add("severity", severity);
             titleFragment.appendChild(severityElement);
         }
         titleFragment.createTextChild(title);
 
         var treeElement = new TreeElement(titleFragment, null, !!result.children);
         parentTreeElement.appendChild(treeElement);
 
         if (result.className)
             treeElement.listItemElement.classList.add(result.className);
         if (typeof result.value !== "string")
             treeElement.listItemElement.appendChild(WebInspector.auditFormatters.apply(result.value));
 
         if (result.children) {
             for (var i = 0; i < result.children.length; ++i)
                 this._appendResult(treeElement, result.children[i]);
         }
         if (result.expanded) {
             treeElement.listItemElement.classList.remove("parent");
             treeElement.listItemElement.classList.add("parent-expanded");
             treeElement.expand();
         }
         return treeElement;
     },
 
     __proto__: WebInspector.SidebarPane.prototype
 }