src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/toGridViewDirection
class EditorPart:	private toGridViewDirection(direction: GroupDirection): Direction {
		switch (direction) {
			case GroupDirection.UP: return Direction.Up;
			case GroupDirection.DOWN: return Direction.Down;
			case GroupDirection.LEFT: return Direction.Left;
			case GroupDirection.RIGHT: return Direction.Right;
		}
	}