Use USB mojo interfaces in chrome/browser/devtools/usb/.

Convert direct UsbService calling in chrome/browser/devtools/usb to
to using mojo interface and and adjust the tests.

Bug: 699790

Change-Id: Ie4e9cd54db6e6fe88538b59bc92105fd9d155f4d
Reviewed-on: https://chromium-review.googlesource.com/c/1329541
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Donna Wu <donna.wu@intel.com>
Cr-Commit-Position: refs/heads/master@{#613802}