src/vs/workbench/browser/contextkeys.ts/WorkbenchContextKeysHandler/getWorkbenchStateString
class WorkbenchContextKeysHandler:	private getWorkbenchStateString(): string {
		switch (this.contextService.getWorkbenchState()) {
			case WorkbenchState.EMPTY: return 'empty';
			case WorkbenchState.FOLDER: return 'folder';
			case WorkbenchState.WORKSPACE: return 'workspace';
		}
	}