fix compile error

src/vs/workbench/browser/layout.ts

@@ -43,8 +43,6 @@ interface PartLayoutInfo {
 	statusbar: { height: number; };
 }
 
-interface ILayoutInternalOptions extends ILayoutOptions { };
-
 /**
  * The workbench layout is responsible to lay out all parts that make the Workbench.
  */

src/vs/workbench/services/part/common/partService.ts

@@ -25,7 +25,7 @@ export enum Position {
 
 export interface ILayoutOptions {
 	toggleMaximizedPanel?: boolean;
-	source: Parts;
+	source?: Parts;
 }
 
 export const IPartService = createDecorator<IPartService>('partService');