Make all emitters readonly

src/common/buffer/BufferSet.ts

@@ -19,7 +19,7 @@ export class BufferSet extends Disposable implements IBufferSet {
   private _alt!: Buffer;
   private _activeBuffer!: Buffer;
 
-  private _onBufferActivate = this.register(new EventEmitter<{activeBuffer: IBuffer, inactiveBuffer: IBuffer}>());
+  private readonly _onBufferActivate = this.register(new EventEmitter<{activeBuffer: IBuffer, inactiveBuffer: IBuffer}>());
   public readonly onBufferActivate = this._onBufferActivate.event;
 
   /**

src/common/buffer/Marker.ts

@@ -15,7 +15,7 @@ export class Marker extends Disposable implements IMarker {
 
   public get id(): number { return this._id; }
 
-  private _onDispose = new EventEmitter<void>();
+  private readonly _onDispose = new EventEmitter<void>();
   public readonly onDispose = this._onDispose.event;
 
   constructor(