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

third_party/WebKit/Source/devtools/front_end/bindings/BreakpointManager.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 39 matching lines @@
     this._breakpointsForUISourceCode = new Map();
     this._breakpointsForPrimaryUISourceCode = new Map();
     /** @type {!Multimap.<string, !WebInspector.BreakpointManager.Breakpoint>} */
     this._provisionalBreakpoints = new Multimap();
 
     this._workspace.addEventListener(WebInspector.Workspace.Events.ProjectRemoved, this._projectRemoved, this);
     this._workspace.addEventListener(WebInspector.Workspace.Events.UISourceCodeAdded, this._uiSourceCodeAdded, this);
     this._workspace.addEventListener(WebInspector.Workspace.Events.UISourceCodeRemoved, this._uiSourceCodeRemoved, this);
 }
 
+/** @enum {symbol} */
 WebInspector.BreakpointManager.Events = {
-    BreakpointAdded: "breakpoint-added",
-    BreakpointRemoved: "breakpoint-removed",
-    BreakpointsActiveStateChanged: "BreakpointsActiveStateChanged"
+    BreakpointAdded: Symbol("breakpoint-added"),
+    BreakpointRemoved: Symbol("breakpoint-removed"),
+    BreakpointsActiveStateChanged: Symbol("BreakpointsActiveStateChanged")
 }
 
 /**
  * @param {string} sourceFileId
  * @param {number} lineNumber
  * @param {number} columnNumber
  * @return {string}
  */
 WebInspector.BreakpointManager._breakpointStorageId = function(sourceFileId, lineNumber, columnNumber)
 {
@@ skipping 1009 matching lines @@
 {
     this.sourceFileId = breakpoint._sourceFileId;
     this.lineNumber = breakpoint.lineNumber();
     this.columnNumber = breakpoint.columnNumber();
     this.condition = breakpoint.condition();
     this.enabled = breakpoint.enabled();
 }
 
 /** @type {!WebInspector.BreakpointManager} */
 WebInspector.breakpointManager;