bug(MatDialog): with 'autoFocus: false' lacks focus trap after angular/material@9.2.1/9.2.2

[trebor292]

Reproduction

Steps to reproduce:

1. Add autoFocus: false to any matDialog stackblitz example with a tabbable element.
2. Tab through and see focus goes beyond the dialog

Expected Behavior

Expected behavior can be seen with the use of @angular/material@9.2.0. The focus trap div is correctly added and tabbing with the dialog open, keeps the focus inside the dialog. Automatically added focus trap div:
<div tabindex="0" class="cdk-visually-hidden cdk-focus-trap-anchor" aria-hidden="true"></div>

Actual Behavior

The div above is nowhere to be seen with angular/material@9.2.1 or 9.2.2, and consevently lets focus move beyond and outside the dialog.

Environment

• Angular/Material: 9.2.1
• Browser(s): Chrome, IE, Edge (any)
• Operating System: Windows

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