bluetooth: Tests refactoring: BaseAdapter, FailStartDiscoveryAdapter...
This is the first step towards refactoring our test platform. Add
BaseAdapter and FailStartDiscoveryAdapter and refactor EmptyAdapter and
DiscoverySession.
The design is specified here:
https://docs.google.com/document/d/1_QsBzcc84SwF7oaBWbO8rBzn39MISQ3w-6QM9hk0L3E/edit?usp=sharing
Blink-side patch: http://crrev.com/
1236583003
BUG=499552
Review URL: https://codereview.chromium.org/
1236073003
Cr-Commit-Position: refs/heads/master@{#339687}