mat-form-field > textarea[matInput] shifts when resized to one row

#### Bug, feature request, or proposal:
When you resize a mat-form-field > textarea[matInput] down to one row, the contents of the textarea animate and shift downward, clipping.

#### What is the expected behavior?
There is no movement in the textarea or its content when it is resized.

#### What is the current behavior?
The content gets clipped.

#### What are the steps to reproduce?
https://stackblitz.com/edit/angular-material2-issue-bg2qqg?file=app/app.component.html

Shorten the textarea

Bug also present on https://material.angular.io/components/form-field/overview

#### What is the use-case or motivation for changing an existing behavior?
A user can easily shorten an expandable textarea and should not have the text shift and clip.

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
Affects head Angular Material 2.

Linux Chrome, OS X Chrome.

But not present on Safari because textarea cannot resize smaller than it is on the demo page (locked at min 2 rows for me), unlike Chrome.

Reproduce the behavior from the linked StackBlitz, starting with app/app.component.html, and compare it with the Angular Material form-field overview demo. Resize textarea[matInput] to one row and verify that the textarea contents no longer move or become clipped.

Written by the indexing model from the issue text.