Refactor and test Android service termination.

Refactor and test Android service termination.

This patch cleans up Android child service termination logic and covers
it with tests.

ChildProcessConnection:
- the contract of calling the ConnectionCallback in
  ChildProcessConnection exactly once after setupConnection() is now
  explicitly enforced
- the pid of the process connection remains valid after the connection
  terminates. This will also make logs more readable.

ChildProcessLauncher:
- cleanup logic is now always handled by DeathCallback, both for
  connections that terminate before and after setup completion
- getChildService() is removed as dead code

ChildProcessService + AIDL:
- crashIntentionallyForTesting() is added to allow to synchronously kill
  a child service

Tests:
- tests create child processes from Java and verify correct cleanup for
  services terminating before setup is initiated and after setup
  completes; as well as for connections that fail the initial bind

BUG=363121
R=clamy@chromium.org, palmer@chromium.org, yfriedman@chromium.org

Review URL: https://codereview.chromium.org/243103002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@265956 0039d316-1c4b-4281-b951-d872f2087c98