bug(Datepicker): Not marked as dirty if first input is an invalid date

[DominicSachs]

Reproduction

Use StackBlitz to reproduce your issue: https://stackblitz.com/edit/angular-ivy-8sjw5j

Steps to reproduce:
If I enter an invalid date like 'aaa' in Datepicker for the first time, then the dirty flag is not set. And then the ShowOnDirtyErrorStateMatcher does not show an error.

With the OnBlur Matcher it is working. Please comment out line 26 in app.component.ts and try it again. Enter 'aaa' and trigger onBlur while you click the tab key.

Expected Behavior

The date control is marked as dirty and the error is shown.

Actual Behavior

No error is displayed because the control is not marked as dirty.

Environment

• Angular: 9.2.4
• CDK/Material: 9.2.4
• Browser(s): Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Windows 10

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