Reduce state in buffer decorations

src/common/services/DecorationService.ts

@@ -17,6 +17,8 @@ export class DecorationService extends Disposable implements IDecorationService
   public get onDecorationRemoved(): IEvent<IInternalDecoration> { return this._onDecorationRemoved.event; }
   private _decorations: IInternalDecoration[] = [];
 
+  public get decorations(): IterableIterator<IInternalDecoration> { return this._decorations.values(); }
+
   constructor() {
     super();
   }

src/common/services/Services.ts

@@ -303,6 +303,7 @@ export interface IUnicodeVersionProvider {
 
 export const IDecorationService = createDecorator<IDecorationService>('DecorationService');
 export interface IDecorationService extends IDisposable {
+  readonly decorations: IterableIterator<IInternalDecoration>;
   readonly onDecorationRegistered: IEvent<IInternalDecoration>;
   readonly onDecorationRemoved: IEvent<IInternalDecoration>;
   registerDecoration(decorationOptions: IDecorationOptions): IDecoration | undefined;