Header not expanding when page height is less than window height

[chadkrause]

What MDL Version are you using? (please be specific, e.g. major.minor.patch)
1.2.1

What browser(s) is this bug affecting (including version)?
All browsers, mobile and desktop

What OS (and version) are you using?
All browsers

What are the steps to reproduce the bug? Can you create a plunker/codepen/jsfiddle which reproduces it?

https://codepen.io/chadkrause308/pen/EgBRKd/?editors=0010#0
Change layout to split screen, as in side by side and not top and bottom

What is the expected behavior?
When you scroll up, the header gets bigger

What is the actual behavior?
When you scroll up, the header stays in the smaller size

Any other information you believe would be useful?
This happens if the page is not longer than the browser window when the header is collapsed. The header is supposed to expand when you scroll up, but it wont since the page isn't longer than the window. To fix this, you have to create a

set that is a height that makes the page larger than the window.

[chadkrause]

Also, you can click on the header to make it bigger, but it is not really user friendly that way. People don't know to do that