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On Linux, the physical device ID is the sysfs path of the device
that best represents the physical device connected to the system.
For USB and Bluetooth devices, this is a device node that
represents the entire physical device as opposed to one particular
HID interface exposed by the device.

For some devices, this cannot be determined because the device
driver does not expose the information or the device is not
physical. For these cases, the sysfs path of the HID interface
is used instead.

BUG=1011499

Change-Id: Ia887baa3dd78c0132d6e9fa0d37791941cd17bda
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1966499Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770760}