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

third_party/WebKit/Source/devtools/front_end/workspace/FileSystemMapping.js

 /*
  * Copyright (C) 2012 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 23 matching lines @@
  */
 WebInspector.FileSystemMapping = function()
 {
     WebInspector.Object.call(this);
     this._fileSystemMappingSetting = WebInspector.settings.createLocalSetting("fileSystemMapping", {});
     /** @type {!Object.<string, !Array.<!WebInspector.FileSystemMapping.Entry>>} */
     this._fileSystemMappings = {};
     this._loadFromSettings();
 }
 
+/** @enum {symbol} */
 WebInspector.FileSystemMapping.Events = {
-    FileMappingAdded: "FileMappingAdded",
-    FileMappingRemoved: "FileMappingRemoved"
+    FileMappingAdded: Symbol("FileMappingAdded"),
+    FileMappingRemoved: Symbol("FileMappingRemoved")
 }
 
 WebInspector.FileSystemMapping.prototype = {
     _loadFromSettings: function()
     {
         var savedMapping = this._fileSystemMappingSetting.get();
         this._fileSystemMappings = {};
         for (var fileSystemPath in savedMapping) {
             var savedFileSystemMappings = savedMapping[fileSystemPath];
             fileSystemPath = WebInspector.IsolatedFileSystemManager.normalizePath(fileSystemPath);
@@ skipping 284 matching lines @@
     this.fileSystemPath = fileSystemPath;
     this.urlPrefix = urlPrefix;
     this.pathPrefix = pathPrefix;
     this.configurable = configurable;
 }
 
 /**
  * @type {!WebInspector.FileSystemMapping}
  */
 WebInspector.fileSystemMapping;