components: Global Disable Ripple Does Not Affect Keyboard Focus

Bug, feature request, or proposal:

Bug.

What is the expected behavior?

When you set disabled: true using RippleGlobalOptions, the ripple should disappear completely, no matter if the focus arrives through tab key on keyboard or through mouse click.

What is the current behavior?

After setting disabled: true using RippleGlobalOptions, the ripple effect still appears when the focus arrives through tab key.

What are the steps to reproduce?

Here is a simple plunker containing two checkboxes: https://plnkr.co/edit/7aqtkq?p=preview

You can see that ripple effect is disabled globally. When you click any checkbox with mouse, the ripple effect does not appear, as expected. However, when you select any checkbox using tab key, the ripple effect still appears.

What is the use-case or motivation for changing an existing behavior?

I guess that when you disable ripple effect, you want to disable it completely.

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

Angular 4, latest version of Material, Windows, browsers Google Chrome, Internet Explorer.

Is there anything else we should know?

One can get rid of the ripple effect completely using css .mat-checkbox-ripple { display: none; }