<Icon> className height/width get overridden if no size is included

[willyrk1]

Do you want to request a feature or report a bug?
Feature, mostly.
What is the current behavior?
If you want to set height/width for an <Icon> using className, you also have to include size='' or else the hard-coded default styles, height: 32, width: 32, will take precedence over your className height/width.
If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Paste the link to your JSFiddle (https://jsfiddle.net/Luktwrdm/) or CodeSandbox (https://codesandbox.io/s/new) example below:

What is the expected behavior?
If the size prop is not specified, it should default to '' (or whatever implementation allows height/width to be set by className without being overridden by hard-coded default styles).
Which versions of MDL, and which browser / OS are affected by this issue? Did this work in previous versions of MDL?
This has presumably always been the behavior.