[DevTools] Fix compile errors before closure compiler roll

third_party/WebKit/Source/devtools/front_end/elements/StylesSidebarPane.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 1138 matching lines @@
     /**
      * @return {boolean}
      */
     _updateFilter: function()
     {
         var hasMatchingChild = false;
         for (var child of this.propertiesTreeOutline.rootElement().children())
             hasMatchingChild |= child._updateFilter();
 
         var regex = this._parentPane.filterRegex();
-        var hideRule = !hasMatchingChild && regex && !regex.test(this.element.textContent);
+        var hideRule = !hasMatchingChild && !!regex && !regex.test(this.element.textContent);
         this.element.classList.toggle("hidden", hideRule);
         if (!hideRule && this._style.parentRule)
             this._markSelectorHighlights();
         return !hideRule;
     },
 
     _markSelectorMatches: function()
     {
         var rule = this._style.parentRule;
         if (!rule)
@@ skipping 1914 matching lines @@
     WebInspector.context.addFlavorChangeListener(WebInspector.DOMNode, onNodeChanged);
     onNodeChanged();
     return button;
 
     function onNodeChanged()
     {
         var node = WebInspector.context.flavor(WebInspector.DOMNode);
         button.setEnabled(!!node);
     }
 }