After selecting an option on md-select it does not adjust width while resizing window

[jfletcher2]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Once the user selects a value on md-select and the browser window is resized the md-select element should adjust its width accordingly. md-input works fine.

What is the current behavior?

The md-select width is not adjusted correctly when the browser window is re-sized.
Full Size window:

Resized window:

What are the steps to reproduce?

Plunker: http://plnkr.co/edit/DiPQWnqp76znq27BmXuj?p=preview

1. If we try resizing the preview window without choosing any options on both "Select Option 1" and "Select Option 2", it should work fine.
2. Choose an option for "Select Option 1" and "Select Option 2" and then try to resize. The select element does not adjust its width automatically like it did when none of the options were selected.

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

The field alignment for md-select is thrown off when the user tries to resize the page.

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

Angular Material (SHA 899f190)
Browser: Chrome

[shlomiassaf]

@jelbourn I created a quick PR for that, see #6684

I wrote an explanation on why and how

[SchnWalter]

At a quick glance, this seem to be related to #5298

[andrewseguin]

Should've been resolved a long time ago by #14932.