Chrome Version       : 55.0.2883.87 (Official Build) unknown (64-bit)

Other browsers tested: N/A

What steps will reproduce the problem?

(1) Build a web app, that is using WebUSB
(2) Open the web app in more than one tab
(3) In one tab, open the device and claim one of the interfaces

What is the expected result?

In the other tabs of the same web app (same URL, same origin, same permissions, ...), I should see the device as opened/interface claimed.

In that way, you can prevent multiple read/write attempts at the same time.

What happens instead?

In the tab you opened the device, the device is seen as opened; but the other device see it with `opened: false` and the interface as not claimed.

You cannot therefore detect that some other tab of the same app is trying to use the device.

You can do it via some other means - for example, by having a shared place in sessionStorage - but that feels hacky.