MdSelect: no scrollbar when initially opening (Chrome and Safari)

[willshowell]

Bug, feature request, or proposal:

Bug

What is the expected behavior?

The scrollbar should be visible in all overflowed selects.

What is the current behavior?

The scrollbar is not visible when the select is placed within a dialog.

What are the steps to reproduce?

https://plnkr.co/edit/vp7LscCgU9X7v165vRPA?p=preview

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

latest, latest, macOS 10.12, latest, Chrome (58.0)

Other

Seems to work perfectly in FF, but Safari does exhibit inconsistent behavior as well - the scroll bar does not initially appear when inside a dialog.

Also note, the spec declares a "persistent scrollbar" should be shown for overflowing menus. That would solve this as well.

[hans-pragt]

I have also been told that other elements don't render when they shown inside a dialog window, specifically when using Chrome in OS X. For instance, in this plunkr the slider track is visible, but the toggle thumb is not.

[willshowell]

I've experienced this again outside of a dialog, so it's now my understanding that it's related to where the select is positioned on the page. See this updated plunk for demo:

https://plnkr.co/edit/4M3t8iHcQ5t2pjd9DWjl?p=preview

[lacolaco]

@crisbeto Any updates on this?