Buttons and input fields appear over/through toolbar

[alltom]

What MDC-Web Version are you using?

23a0a12

What browser(s) is this bug affecting?

Chrome 58.0.3013.3 (Official Build) dev (64-bit)

What OS are you using?

macOS Sierra 10.12.3 (16D32)

What are the steps to reproduce the bug?

1. Add a fixed toolbar by copying the demo.
2. Add mdc-buttons, mdc-textfields, etc to the body.
3. Scroll.

What is the expected behavior?

The toolbar occludes the buttons and text fields.

What is the actual behavior?

They show through:

But regular text does not.

[Garbee]

We need a z-index on the toolbar. For some reason elements are being layered up that shouldn't (clearly) be.

[traviskaufman]

Thanks for reporting! Looks like relatively-positioned elements are showing up on top of a fixed-position toolbar shrugs.

[alltom]

Thank you. :)