src/vs/editor/contrib/dnd/dnd.ts/DragAndDropController/_hitMargin
class DragAndDropController:	private _hitMargin(target: IMouseTarget): boolean {
		return target.type === MouseTargetType.GUTTER_GLYPH_MARGIN ||
			target.type === MouseTargetType.GUTTER_LINE_NUMBERS ||
			target.type === MouseTargetType.GUTTER_LINE_DECORATIONS;
	}