feat(SnackBar): allow easily reuse action styles for openFromComponent/openFromTemplate

[evil-shrike]

Feature Description

Please provide styles for using standard SnackBar layout in custom ones. Specifically classes mat-simple-snackbar and mat-simple-snackbar-action so users can easily add action button in their custom snackbar with same look&feel.

Use Case

From three open methods only the one support passing an action - open:

snackBar.open('message', 'Dismiss');
snackBar.openFromComponent(CustomSnackBar, { data: { message: "message"} });
snackBar.openFromTemplate(this.snackbarTemplate);

it's understandable as the two others allow to customize layouts and this is exactly why we need them.
But, let's suppose I need a custom layout and a Dismiss button. I should choose between openFromComponent and openFromTemplate methods and then implement the dismiss button in my markup.
The problem is that I want the same look and feed as in snackbars that opened via the open method.

I tried to use SB's standard styles:

<div class="mat-simple-snackbar">
  <span>{{ data.message }}</span>
  <div class="mat-simple-snackbar-action">
    <button mat-icon-button (click)="sbRef.dismiss()">
      <span class="mat-button-wrapper">Dismiss</span>
    </button>
  </div>
</div>

but it doesn't work as it seems the styles are being added dynamically when a new SnackBar is opened via open.
BTW it creats an inconsistent behavior when I open my custom snackbar, then a standard one and then again my own. The latter will have a different layout then the first one (probably because of some dynamically added styles left).

[angular-robot]

Just a heads up that we kicked off a community voting process for your feature request. There are 20 days until the voting process ends.

Find more details about Angular's feature request process in our documentation.

[angular-robot]

Thank you for submitting your feature request! Looks like during the polling process it didn't collect a sufficient number of votes to move to the next stage.

We want to keep Angular rich and ergonomic and at the same time be mindful about its scope and learning journey. If you think your request could live outside Angular's scope, we'd encourage you to collaborate with the community on publishing it as an open source package.

You can find more details about the feature request process in our documentation.