Elements of the MatPortalHost are not themed by a MatThemeProvider

[Qubitza]

Placing a MatPortalHost into a MatThemeProvider doesn't apply the defined MatTheme on dialog elements (e.g. the popup of a DatePicker)

To Reproduce
Place a MatPortalHost into a MatThemeProvider and apply a theme.
The generated div when opening the DateTime dialog will not be themed, as the class does not include the matBlazor_theme_*.

Blazorfiddle link
https://blazorfiddle.com/s/oe3258v9
Somehow, the fiddle did not work on my machine. However, you can see the code.

Expected behavior
The generated theme class (e.g. matBlazor_theme_2f29a5a8-9fda-4b2e-9332-9eb2089efe1c in the screenshot) is applied to elements which are created by the MatPortalHost.

Screenshots