fixes#5390
Before the change:
// original CSS
:host .foo .bar {...}
.foo .bar {...}
// translated to
[_nghost-shh-2] .foo .bar {...}
.foo[_ngcontent-shh-2] .bar[_ngcontent-shh-2] {...}
Note that `.foo` and `.bar` where not scoped and would then apply to nested components.
With this change those selectors are scoped (as they are without `:host`).
You can explicitly apply the style to inner component by using `>>>` or `/deep/`: `:host >>> .foo`
Victor Berchet
af63378fa0