Cherry pick from https://googleplex-android-review.git.corp.google.com/#/c/398226/
This adds an integer to the descriptor of devices without uniqely
identifying information. It will reuse values that are no longer
in use, so if you remove a single device and attach a different
identical device it will appear to be the same device.
TODO: Derive uniqueness from USB port when possible. This version
will generate different descriptors for each half of a USB keyboard
that shows up twice.
Change-Id: Ie628f19c01469f6ec2d354cd00000898ac6432fa
Refactored the directory structure so that services can be optionally
excluded. This is step 1. Will be followed by another change that makes
it possible to remove services from the build.
Change-Id: Ideacedfd34b5e213217ad3ff4ebb21c4a8e73f85
