grid - add editor index to group change event

src/vs/workbench/browser/parts/editor2/nextEditorGroupView.ts

@@ -410,7 +410,7 @@ export class NextEditorGroupView extends Themable implements INextEditorGroupVie
 
 		// Event
 		this._onDidCloseEditor.fire(event);
-		this._onDidGroupChange.fire({ kind: GroupChangeKind.EDITOR_CLOSE, editor });
+		this._onDidGroupChange.fire({ kind: GroupChangeKind.EDITOR_CLOSE, editor, editorIndex: event.index });
 	}
 
 	private onDidEditorDispose(editor: EditorInput): void {

src/vs/workbench/services/group/common/nextEditorGroupsService.ts

@@ -254,6 +254,7 @@ export enum GroupChangeKind {
 export interface IGroupChangeEvent {
 	kind: GroupChangeKind;
 	editor?: IEditorInput;
+	editorIndex?: number;
 }
 
 export interface INextEditorGroup {