If the cursor is moved with a USB mouse, Input.GetAxis("Mouse X") and Input.GetAxis("Mouse Y") return 0 if the cursor is moved with the built-in touchpad afterwards. If mouse isn't moved, using the touchpad returns expected values.

Steps to reproduce:
- Make sure you have a USB mouse connected to the MacBook (wired, not Bluetooth).
1) Open the latest attached project.
2) Press play.
3) Without moving the mouse, swipe across the touchpad.
- Notice the Input.GetAxis values changing on the screen.
4) Move the mouse around a bit.
5) Swipe on the touchpad again.

The input values do not change - if the USB mouse is moved, no further input from the touchpad is registered with Input.GetAxis. This does not occur on Windows laptops. Happens in the Editor and on standalone builds.

Reproduced on:
5.6.0a2, 5.4.2p4, 5.2.4f1

Tested on:
MacBook Pro Early 2013 and MacBook Pro Mid 2015 + Gigabyte GM-M6800