Input gets stuck in focused mode when disabled on Firefox

[benelliott]

Bug, feature request, or proposal:

If you disable an input in its focus handler, it will correctly appear as disabled on Chrome but will get stuck in its "focused mode" (floating placeholder) on Firefox 57.

What is the expected behavior?

Not to be stuck

What is the current behavior?

Gets stuck on Firefox

What are the steps to reproduce?

Providing a StackBlitz/Plunker (or similar) is the best way to get the team to see your issue.

Plunker starter (using on @master): https://goo.gl/uDmqyY

StackBlitz starter (using latest npm release): https://goo.gl/wwnhMV

Plunker: http://plnkr.co/edit/ldcUfXWmq7N6BU6HPcBA?p=preview
StackBlitz: https://stackblitz.com/edit/angular-material2-issue-dqxr2d?file=app/app.component.ts

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

Consistency across browsers.

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

Master (Version: 5.0.0-rc.1-6e865b7) and 5.0.0-rc0

Is there anything else we should know?

Firefox 57 is a big change so could be a browser issue?

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