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

third_party/WebKit/Source/devtools/front_end/sdk/Script.js

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 41 matching lines @@
     this.endLine = endLine;
     this.endColumn = endColumn;
     this._executionContextId = executionContextId;
     this.hash = hash;
     this._isContentScript = isContentScript;
     this._isLiveEdit = isLiveEdit;
     this.sourceMapURL = sourceMapURL;
     this.hasSourceURL = hasSourceURL;
 }
 
+/** @enum {symbol} */
 WebInspector.Script.Events = {
-    ScriptEdited: "ScriptEdited",
-    SourceMapURLAdded: "SourceMapURLAdded"
+    ScriptEdited: Symbol("ScriptEdited"),
+    SourceMapURLAdded: Symbol("SourceMapURLAdded")
 }
 
 WebInspector.Script.sourceURLRegex = /^[\040\t]*\/\/[@#] sourceURL=\s*(\S*?)\s*$/m;
 
 /**
  * @param {string} source
  * @return {string}
  */
 WebInspector.Script._trimSourceURLComment = function(source)
 {
@@ skipping 258 matching lines @@
             {
                 if (error)
                     console.error(error);
                 fulfill(!error);
             }
         }
     },
 
     __proto__: WebInspector.SDKObject.prototype
 }