mat-expansion-panel animates expanded to closed when nested in a mat-dialog

[WrongWayJerry]

Bug, feature request, or proposal:

With Angular 7 the mat-expansion-panel when it is in a mat-dialog will "flash" from expanded to closed when the dialog is initially displayed.

What is the expected behavior?

Should behave like Angular 6 and should not show as expanded and then immediately close when a dialog is opened.

What is the current behavior?

When displaying a mat-dialog the expansion panel will display its contents expanded and then immediately close.

What are the steps to reproduce?

Providing a StackBlitz reproduction is the best way to share your issue.

StackBlitz starter: https://goo.gl/wwnhMV

https://angular-wlrqxn.stackblitz.io

If you cannot open the sample add the following code to the mat-dialog example on the Angular 7 site - stackblitz example:

https://stackblitz.com/angular/koppvkvpmpdn?file=app%2Fdialog-overview-example-dialog.html

<div mat-dialog-content>
  <p>What's your favorite animal?</p>
  <mat-form-field>
    <input matInput [(ngModel)]="data.animal">
  </mat-form-field>
  <mat-expansion-panel>
        <mat-expansion-panel-header>
            <mat-panel-title>
                Hello
            </mat-panel-title>
        </mat-expansion-panel-header>
        <mat-card-content>
          <div>World!</div>
          <div>World!</div>
          <div>World!</div>
          <div>World!</div>
          <div>World!</div>
        </mat-card-content>
  </mat-expansion-panel>
</div>

What is the use-case or motivation for changing an existing behavior?

The content of the expansion panel should not display if the panel is closed.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Angular 7,
Windows
Firefox and Chrome

Is there anything else we should know?

[manklu]

Duplicate of #13870

[crisbeto]

Closing as a duplicate.

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