Emulated Encapsulation Host And Content Attributes Are Calculated Once Per Component Type In Angular 6.1.10

snippet.css

.selected[ _nghost-c2 ] label[ _ngcontent-c2 ] {
	color: red ;
}

snippet.htm

<my-tree-node _nghost-c2>
	<my-tree-node _nghost-c2 _ngcontent-c2>
		<my-tree-node _nghost-c2 _ngcontent-c2>
			<my-tree-node _nghost-c2 _ngcontent-c2>
				<!-- ... -->
			</my-tree-node>
		</my-tree-node>
	</my-tree-node>
</my-tree-node>