[android log] Add documentation and presubmit checks for log usage.

[android log] Add documentation and presubmit checks for log usage.

The new check warns for new log usages that don't use base.Log

The documentation is added in-tree as a markdown file

BUG=472152
Committed: https://crrev.com/4401aa59eab219cf6f9c040ee23a8fc80b3efbaf
Cr-Commit-Position: refs/heads/master@{#327504}

[dgn, 2015-04-28 17:05:55]

dgn@chromium.org changed reviewers:
+ bauerb@chromium.org, jochen@chromium.org, yfriedman@chromium.org

[dgn, 2015-04-28 17:05:55]

jochen@: PTAL at the changes in PRESUBMIT

bauerb@, yfriedman@: PTAL at the new logging documentation. It is copied from
the internal one, since there is nothing private inside and it has to be
referenced from the presubmit message. I made it as markdown as we need a
replacement for the wiki and some pages have been moved to markdown already.

[jochen (gone - plz use gerrit), 2015-04-28 19:01:38]

lgtm

[Yaron, 2015-04-28 21:51:15]

lgtm

[dgn, 2015-04-29 16:18:11]

The CQ bit was checked by dgn@chromium.org

[commit-bot: I haz the power, 2015-04-29 16:18:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1114593002/1

[commit-bot: I haz the power, 2015-04-29 16:26:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-29 16:27:22]

Patchset 1 (id:??) landed as
https://crrev.com/4401aa59eab219cf6f9c040ee23a8fc80b3efbaf
Cr-Commit-Position: refs/heads/master@{#327504}