Devtools: Fix appearance of PropertiesWidget in ElementPanel

Source/devtools/front_end/elements/PropertiesWidget.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2014 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 138 matching lines @@
             this.sections = [];
 
             // Get array of prototype user-friendly names.
             for (var i = 0; i < prototypes.length; ++i) {
                 if (!parseInt(prototypes[i].name, 10))
                     continue;
                 var prototype = prototypes[i].value;
                 var title = prototype.description;
                 title = title.replace(/Prototype$/, "");
                 var section = new WebInspector.ObjectPropertiesSection(prototype, title);
+                section.element.classList.add("properties-widget-section");
                 this.sections.push(section);
                 this.element.appendChild(section.element);
                 if (expanded[this.sections.length - 1])
                     section.expand();
             }
 
             finishCallback();
         }
     },
 
     /**
      * @param {!WebInspector.Event} event
      */
     _onNodeChange: function(event)
     {
         if (!this._node)
             return;
         var data = event.data;
         var node = /** @type {!WebInspector.DOMNode} */ (data instanceof WebInspector.DOMNode ? data : data.node);
         if (this._node !== node)
             return;
         this.update();
     },
 
     __proto__: WebInspector.ThrottledWidget.prototype
 }