Object properties with values of Symbol type should not be expandable.

Source/devtools/front_end/sdk/RemoteObject.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 204 matching lines @@
     this._target = target;
     this._runtimeAgent = target.runtimeAgent();
     this._domModel = target.domModel;
 
     this._type = type;
     this._subtype = subtype;
     if (objectId) {
         // handle
         this._objectId = objectId;
         this._description = description;
-        this._hasChildren = true;
+        this._hasChildren = this._type === "symbol" ? false : true;

[aandrey, 2014/06/17 12:29:37]

this._hasChildren = (type !== "symbol");

[Alexandra Mikhaylova, 2014/06/17 12:32:29]

Done.

         this._preview = preview;
     } else {
         // Primitive or null object.
         console.assert(type !== "object" || value === null);
         this._description = description || (value + "");
         this._hasChildren = false;
         // Handle special numbers: NaN, Infinity, -Infinity, -0.
         if (type === "number" && typeof value !== "number")
             this.value = Number(value);
         else
@@ skipping 772 matching lines @@
             result = functionDeclaration.apply(target, rawArgs);
         } catch (e) {
             result = null;
         }
 
         callback(result);
     },
 
     __proto__: WebInspector.RemoteObject.prototype
 }