Bug, feature request, or proposal:
proposal
What is the expected behavior?
Material shadow for the toolbar, users might write their own styles to simulate Material shadow for the toolbar, but it would be better if we can define it and users can just activate it easily.

(source)
What is the current behavior?
(as far as I know) there is not any shadow for the toolbar
Current Angular Material Toolbar
What is the use-case or motivation for changing an existing behavior?
To follow Material rules, and provide high-quality shadow (as Material describe) for toolbar