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

third_party/WebKit/Source/devtools/front_end/source_frame/SourceFrame.js

 /*
  * Copyright (C) 2011 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 45 matching lines @@
     this.element.addEventListener("keydown", this._handleKeyDown.bind(this), false);
 
     this._sourcePosition = new WebInspector.ToolbarText();
 
     /**
      * @type {?WebInspector.SearchableView}
      */
     this._searchableView = null;
 }
 
+/** @enum {symbol} */
 WebInspector.SourceFrame.Events = {
-    ScrollChanged: "ScrollChanged",
-    SelectionChanged: "SelectionChanged",
-    JumpHappened: "JumpHappened"
+    ScrollChanged: Symbol("ScrollChanged"),
+    SelectionChanged: Symbol("SelectionChanged"),
+    JumpHappened: Symbol("JumpHappened")
 }
 
 WebInspector.SourceFrame.prototype = {
     /**
      * @param {number} key
      * @param {function():boolean} handler
      */
     addShortcut: function(key, handler)
     {
         this._shortcuts[key] = handler;
@@ skipping 632 matching lines @@
     /**
      * @override
      * @param {?WebInspector.TextRange} from
      * @param {?WebInspector.TextRange} to
      */
     onJumpToPosition: function(from, to)
     {
         this._sourceFrame.onJumpToPosition(from, to);
     }
 }