toggles selection doesn't work pressing the SHIFT key

MDL Version: 1.3.0

Tested and reproduced on FF (45.7.0).
On Chrome (56.0.2924.87) works but inconsistently.
It works 100% on IE 11.

OS:
Windows 7

Steps to reproduce:
Go here: https://getmdl.io/components/index.html#toggles-section
While pressing the "SHIFT" key try to click on some toggle (i.e. a checkbox).

Expected behaviour:
The checkbox should be selected/unselected even when the "SHIFT" key is pressed.

What happens:
On FF the checkbox is never selected/unselected, on Chrome works but inconsistently. on IE 11 works 100%.

Other info:
This would help to implement some kind of "multiple" selection of elements (shift clicking).