Run mojo unit tests on the Android main waterfall.

Run mojo unit tests on the Android main waterfall.

Run Mojo additional unit tests on the "Android GN" bot:
http://build.chromium.org/p/chromium.linux/builders/Android%20GN
(No CQ yet; need Android GN testing support/devices there...)
Add the necessary target mappings to ninja_to_gn.pyl

Similar tests already run on Linux GN and our chromium.mojo FYI:
http://build.chromium.org/p/chromium.linux/builders/Linux%20GN
http://build.chromium.org/p/chromium.mojo/builders/Chromium%20Mojo%20Android

BUG=478244,359249
TEST=Steps run and pass on the bot.
R=dpranke@chromium.org

Review URL: https://codereview.chromium.org/1145343005

Cr-Commit-Position: refs/heads/master@{#335112}