maybe something changed in USB. Maybe it's something else?

I replaced half of the Linux/Chrome OS code for USB yesterday but that shouldn't have affected Windows.

You are probably looking for a change made after 387312 (known good), but no later than 387317 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/08b5f54..781c586?pretty=fuller

likely https://codereview.chromium.org/1877503003

reverting fed1de7faf5d91a3282d461fd1c0657f8fe3a533 on my local build fixes this issue so I'm going to go ahead and revert, since not having u2f working is a bit of a pain for our Canary users.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3

commit 4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3
Author: wfh <wfh@chromium.org>
Date: Fri Apr 15 21:37:29 2016

Revert of Replace libusb in the Linux/Chrome OS USB I/O path. (patchset #3 id:60001 of https://codereview.chromium.org/1877503003/ )

Reason for revert:
broke u2f see  crbug.com/603962 

Original issue's description:
> Replace libusb in the Linux/Chrome OS USB I/O path.
>
> As a first step in adding support for connecting to USB devices on
> Android this patch replaces the libusb-based implementation of
> UsbDeviceHandle used on Linux and Chrome OS with one written directly to
> the Linux usbdevfs ioctl interface.
>
> BUG=422562, 601627 
>
> Committed: https://crrev.com/fed1de7faf5d91a3282d461fd1c0657f8fe3a533
> Cr-Commit-Position: refs/heads/master@{#387315}

TBR=juncai@chromium.org,reillyg@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=422562, 601627 , 603962 

Review URL: https://codereview.chromium.org/1897483003

Cr-Commit-Position: refs/heads/master@{#387704}

[modify] https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3/device/usb/BUILD.gn
[modify] https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3/device/usb/usb.gyp
[modify] https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3/device/usb/usb_device_handle.h
[modify] https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3/device/usb/usb_device_handle_unittest.cc
[delete] https://crrev.com/1b17dc30c89fc6a7a70a490ac942e853537fc2b9/device/usb/usb_device_handle_usbfs.cc
[delete] https://crrev.com/1b17dc30c89fc6a7a70a490ac942e853537fc2b9/device/usb/usb_device_handle_usbfs.h
[modify] https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3/device/usb/usb_device_impl.cc
[modify] https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3/device/usb/usb_device_impl.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2f3b6285b45d43141dfc72131dd81702e4342f85

commit 2f3b6285b45d43141dfc72131dd81702e4342f85
Author: reillyg <reillyg@chromium.org>
Date: Wed Apr 20 01:47:27 2016

Reland of Replace libusb in the Linux/Chrome OS USB I/O path. (patchset #1 id:1 of https://codereview.chromium.org/1897483003/ )

Reason for revert:
Fixed Windows/OS X issue.

Original issue's description:
> Revert of Replace libusb in the Linux/Chrome OS USB I/O path. (patchset #3 id:60001 of https://codereview.chromium.org/1877503003/ )
>
> Reason for revert:
> broke u2f see  crbug.com/603962 
>
> Original issue's description:
> > Replace libusb in the Linux/Chrome OS USB I/O path.
> >
> > As a first step in adding support for connecting to USB devices on
> > Android this patch replaces the libusb-based implementation of
> > UsbDeviceHandle used on Linux and Chrome OS with one written directly to
> > the Linux usbdevfs ioctl interface.
> >
> > BUG=422562, 601627 
> >
> > Committed: https://crrev.com/fed1de7faf5d91a3282d461fd1c0657f8fe3a533
> > Cr-Commit-Position: refs/heads/master@{#387315}
>
> TBR=juncai@chromium.org,reillyg@chromium.org
> # Not skipping CQ checks because original CL landed more than 1 days ago.
> BUG=422562, 601627 , 603962 
>
> Committed: https://crrev.com/4ee09b3e7eab98835bc1a47c55f3b3080c2f5fd3
> Cr-Commit-Position: refs/heads/master@{#387704}

# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=422562, 601627 , 603962 

Review URL: https://codereview.chromium.org/1902313002

Cr-Commit-Position: refs/heads/master@{#388402}

[modify] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/BUILD.gn
[modify] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb.gyp
[modify] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb_device_handle.h
[modify] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb_device_handle_unittest.cc
[add] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb_device_handle_usbfs.cc
[add] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb_device_handle_usbfs.h
[modify] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb_device_impl.cc
[modify] https://crrev.com/2f3b6285b45d43141dfc72131dd81702e4342f85/device/usb/usb_device_impl.h