Isolate device_unittests.

This is a pretty mechanical change because device_unittests only depends
on //base and //device. Just in case USB gadget tests are enabled on the
swarming bots usb_gadget.zip is included in device_unittests.isolate.

BUG=98637

Review URL: https://codereview.chromium.org/1217563004

Cr-Commit-Position: refs/heads/master@{#336908}
8 files changed