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

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

 // Copyright (c) 2015 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.
 
 /**
  * @extends {WebInspector.Object}
  * @constructor
  */
 WebInspector.ComputedStyleModel = function()
 {
     WebInspector.Object.call(this);
     this._node = WebInspector.context.flavor(WebInspector.DOMNode);
     WebInspector.context.addFlavorChangeListener(WebInspector.DOMNode, this._onNodeChanged, this);
 }
 
+/** @enum {symbol} */
 WebInspector.ComputedStyleModel.Events = {
-    ComputedStyleChanged: "ComputedStyleChanged"
+    ComputedStyleChanged: Symbol("ComputedStyleChanged")
 }
 
 WebInspector.ComputedStyleModel.prototype = {
     /**
      * @return {?WebInspector.DOMNode}
      */
     node: function()
     {
         return this._node;
     },
@@ skipping 134 matching lines @@
 /**
  * @constructor
  * @param {!WebInspector.DOMNode} node
  * @param {!Map.<string, string>} computedStyle
  */
 WebInspector.ComputedStyleModel.ComputedStyle = function(node, computedStyle)
 {
     this.node = node;
     this.computedStyle = computedStyle;
 }