DevTools: Use JS symbols instead of strings for eligible events.

third_party/WebKit/Source/devtools/front_end/common/Console.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @extends {WebInspector.Object}
  */
 WebInspector.Console = function()
 {
     /** @type {!Array.<!WebInspector.Console.Message>} */
     this._messages = [];
 }
 
-/**
- * @enum {string}
- */
+/** @enum {symbol} */
 WebInspector.Console.Events = {
-    MessageAdded: "messageAdded"
+    MessageAdded: Symbol("messageAdded")
 }
 
 /**
  * @enum {string}
  */
 WebInspector.Console.MessageLevel = {
     Log: "log",
     Warning: "warning",
     Error: "error"
 }
@@ skipping 68 matching lines @@
      */
     showPromise: function()
     {
         return WebInspector.Revealer.revealPromise(this);
     },
 
     __proto__: WebInspector.Object.prototype
 }
 
 WebInspector.console = new WebInspector.Console();