Google Chrome	72.0.3593.0 (Official Build) dev (64-bit)
Firmware Version	Google_Caroline.7820.384.0

Open Calculator app
Attempt to use the tab key or arrow keys to put focus on the buttons to press them

Expected: way to use the buttons, especially ones that don't have keyboard equivalents like anything in the colored drawers 
Actual: no way to access those functions with keyboard only

The basic number and operator buttons are also important to be used by the keyboard for application in future a11y features.