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

third_party/WebKit/Source/devtools/front_end/sdk/CSSParser.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.CSSParser = function()
 {
     this._rules = [];
     this._terminated = false;
 }
 
+/** @enum {symbol} */
 WebInspector.CSSParser.Events = {
-    RulesParsed: "RulesParsed"
+    RulesParsed: Symbol("RulesParsed")
 }
 
 WebInspector.CSSParser.prototype = {
     /**
      * @param {!WebInspector.CSSStyleSheetHeader} styleSheetHeader
      * @param {function(!Array.<!WebInspector.CSSParser.Rule>)=} callback
      */
     fetchAndParse: function(styleSheetHeader, callback)
     {
         this._lock();
@@ skipping 158 matching lines @@
     this.nameRange;
     /** @type {string} */
     this.value;
     /** @type {!WebInspector.CSSParser.Range} */
     this.valueRange;
     /** @type {!WebInspector.CSSParser.Range} */
     this.range;
     /** @type {(boolean|undefined)} */
     this.disabled;
 }