md-list-icon does not resize for dense list

[willshowell]

What is the expected behavior?

Although the spec does not explicitly mention icon sizing, it can be seen that the icon size decreases from 24px to 20px when going from standard to dense lists.

What is the current behavior?

Icons in a dense list look a little lopsided.

What are the steps to reproduce?

http://plnkr.co/edit/TMb2caIf5PhF5xVBjXF2?p=preview

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}