Seems it's not working for me...
I am using a MacbookPro and my gamepad is an Wireless Xbox360 gamepad connected to the Microsoft Wireless receiver.
The controller works on Mac, Steam on Mac, Windows 10 on Bootcamp, Windows on Parallels, Steam for Windows as well as on Firefox and Chrome when going to http://html5gamepad.com/ for the testing.
In Construct 2 it works on the example project running in Edge and Chrome via Bootcamp.
I've made sure Chrome gamepad support is also set to Enabled although I am sure it's enabled in Default mode anyway.
Made text just displaying "Text" that would change if it's supported to "Supported" to "Connected" if any Gamepad is Connected.
I see it change to "supported" but not to connected i've followed the way it's done in C2 as well (Not much to it really). I've tried changing it to Gamepad 1 from Gamepad 0 etc. No dice.
Anyone else tested this yet?