src/vs/workbench/contrib/mergeEditor/browser/view/mergeEditor.ts/MergeEditorLayout/constructor
class MergeEditorLayout:	constructor(@IStorageService private _storageService: IStorageService) {
		const value = _storageService.get(MergeEditorLayout._key, StorageScope.PROFILE, 'mixed');
		if (value === 'mixed' || value === 'columns') {
			this._value = value;
		} else {
			this._value = 'mixed';
		}
	}