Cannot set max-width of the layout grid using a Sass variable

[tinrab]

What MDC-Web Version are you using?

v0.16.0

What are the steps to reproduce the bug?

1. set max width inside demos/demos.scss file before importing MDC.

$mdc-layout-grid-max-width: 300px;
@import "../../material-components-web/material-components-web";

2. run the demo server
3. navigate to http://localhost:8080/layout-grid.html
4. observe the grid's width

What is the expected behavior?

Compiled class mdc-layout-grid should contain max-width property with expected value.

What is the actual behavior?

Setting $mdc-layout-grid-max-width variable, as described in documentation for Layout Grids, does not restrict max width of the layout grid.