MatStepper treats steps as `interacted` if you immediately return to a previous step

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Angular-material forms should be presented in a non-error state when the conditions of the default ErrorStateMatcher are not met (not touched or not submitted)

What is the current behavior?

When a form is presented inside a mat-stepper, when traversing to a previous step, the form will be in an error state even if the form is pristine and un-submitted. Any attempt to try to reset the form or FormGroupDirective fails.

What are the steps to reproduce?

https://stackblitz.com/edit/angular-material2-issue-fay224

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

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

Is there anything else we should know?

リンクされた StackBlitz の再現から始め、前のステップに戻ったときの MatStepper とフォームおよびデフォルトの ErrorStateMatcher の相互作用を追跡します。完了の条件は、未変更で未送信のフォームがステップに再訪した際もエラー状態にならず、フォームまたは FormGroupDirective のリセットが期待どおりに機能することです。