[DevTools] Introduce typed events.

third_party/WebKit/Source/devtools/front_end/resources/DatabaseModel.js

 /*
  * Copyright (C) 2007, 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
@@ skipping 146 matching lines @@
     this._agent.enable();
     this._enabled = true;
   }
 
   disable() {
     if (!this._enabled)
       return;
     this._enabled = false;
     this._databases = [];
     this._agent.disable();
-    this.dispatchEventToListeners(Resources.DatabaseModel.Events.DatabasesRemoved);
+    this.emit(new Resources.DatabaseModel.DatabasesRemovedEvent());
   }
 
   /**
    * @return {!Array.<!Resources.Database>}
    */
   databases() {
     var result = [];
     for (var database of this._databases)
       result.push(database);
     return result;
   }
 
   /**
    * @param {!Resources.Database} database
    */
   _addDatabase(database) {
     this._databases.push(database);
-    this.dispatchEventToListeners(Resources.DatabaseModel.Events.DatabaseAdded, database);
+    this.emit(new Resources.DatabaseModel.DatabaseAddedEvent(database));
   }
 };
 
-/** @enum {symbol} */
-Resources.DatabaseModel.Events = {
-  DatabaseAdded: Symbol('DatabaseAdded'),
-  DatabasesRemoved: Symbol('DatabasesRemoved')
+Resources.DatabaseModel.DatabaseAddedEvent = class {

[lushnikov, 2016/12/15 04:28:59]

maybe we can keep a list of events - it was extremely convenient

[dgozman, 2016/12/16 04:17:46]

JSCompiler didn't like it :-(

+  /**
+   * @param {!Resources.Database} database
+   */
+  constructor(database) {
+    this.database = database;
+  }
 };
 
+Resources.DatabaseModel.DatabasesRemovedEvent = class {};
+
 /**
  * @implements {Protocol.DatabaseDispatcher}
  * @unrestricted
  */
 Resources.DatabaseDispatcher = class {
   /**
    * @param {!Resources.DatabaseModel} model
    */
   constructor(model) {
     this._model = model;
   }
 
   /**
    * @override
    * @param {!Protocol.Database.Database} payload
    */
   addDatabase(payload) {
     this._model._addDatabase(
         new Resources.Database(this._model, payload.id, payload.domain, payload.name, payload.version));
   }
 };
 
 Resources.DatabaseModel._symbol = Symbol('DatabaseModel');