Introduce Disposable abstract class

src/EventEmitter.ts

@@ -5,11 +5,13 @@
 
 import { XtermListener } from './Types';
 import { IEventEmitter, IDisposable } from 'xterm';
+import { Disposable } from './common/Lifecycle';
 
-export class EventEmitter implements IEventEmitter, IDisposable {
+export class EventEmitter extends Disposable implements IEventEmitter, IDisposable {
   private _events: {[type: string]: XtermListener[]};
 
   constructor() {
+    super();
     // Restore the previous events if available, this will happen if the
     // constructor is called multiple times on the same object (terminal reset).
     this._events = this._events || {};
@@ -26,6 +28,7 @@ export class EventEmitter implements IEventEmitter, IDisposable {
    * @param handler The handler for the listener.
    */
   public addDisposableListener(type: string, handler: XtermListener): IDisposable {
+    // TODO: Rename addDisposableEventListener to more easily disambiguate from Dom listener
     this.on(type, handler);
     return {
       dispose: () => {