I have a Dell XPS 13 (2015) which I just upgraded to Windows 10. I can no longer scroll using two-finger drag on the touchpad when in Google Inbox, using Chrome 45.0.2454.15. I can still scroll using the scroll bar on the right, and my touch screen.
This goes for reading individual emails, viewing the entire list, and my chat contacts on the right.
I don't seem to have the issue on other websites.