angular element with overlay rendered in overlay

#### Reproduction

https://github.com/rcketscientist/AngularElementOverlayRepro

Steps to reproduce:
1. Create an Angular Element that leverages a CdkOverlay Material widget (tooltip, select, etc)
2. Place that selector in a CdkOverlay (MatDialog, for example).

As soon you interact with the "inner" CdkOverlay by hovering over the tooltip or activating the select, the host CdkOverlay will just crash without an error message I can pick up on.

This might not really be a bug, but rather a limitation of Angular Elements, but being that it can be triggered with simple widgets I wonder if there's not some way I can get the Angular Elements to play well with the host.

The Angular Elements work fine when not hosted in a CdkOverlay.


#### Expected Behavior

What behavior were you expecting to see?
CdkOverlay within Angular Element plays well with the host.

#### Actual Behavior

What behavior did you actually see?
Acitvation of the CdkOverlay within an Angular Element causes the host CdkOverlay to silently crash.

#### Environment

- Angular:8
- CDK/Material: 8
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Win/Mac

Beginnen Sie mit der Reproduktion unter https://github.com/rcketscientist/AngularElementOverlayRepro und reproduzieren Sie den Fehler mit Angular 8, CDK/Material 8 und Chrome. Untersuchen Sie die Interaktion zwischen dem CDK Overlay-Widget eines Angular Element und seinem Host-Overlay; abgeschlossen ist die Aufgabe, wenn die Tooltip- oder Select-Interaktion das Host-Overlay nicht mehr unbemerkt zum Absturz bringt oder die Einschränkung dokumentiert ist.

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