src/vs/workbench/services/history/browser/historyService.ts/EditorNavigationStack/setIndex
class EditorNavigationStack:	private setIndex(newIndex: number, skipEvent?: boolean): void {
		this.previousIndex = this.index;
		this.index = newIndex;

		// Event
		if (!skipEvent) {
			this._onDidChange.fire();
		}
	}