Revert of Remove mojo test step from bb_device_steps.py (patchset #2 id:20001 of...

Revert of Remove mojo test step from bb_device_steps.py (patchset #2 id:20001 of https://codereview.chromium.org/679553002/)

Reason for revert:
Breaks https://build.chromium.org/p/chromium.linux/builders/Android%20Tests/builds/16413
and
https://build.chromium.org/p/chromium.linux/builders/Android%20Tests%20%28dbg%29/builds/23666
like this:
build/android/buildbot/bb_device_steps.py '--factory-properties={"generate_gtest_json": true, "target": "Release", "gclient_env": {}, "build_url": "gs://chromium-android/android_main_rel", "clobber": false, "GYP_DEFINES": " component=static_library", "target_os": "android", "android_bot_id": "main-tests-rel"}' '--build-properties={"parentname": "Android Builder", "parent_wk_revision": "184325", "parent_got_v8_revision": "24827", "got_swarming_client_revision": "bcb3bc30328c38441d3f7656cb649b123803726c", "parent_build_archive_url": "gs://chromium-android/android_main_rel/full-build-linux_66e8568f2fc06dd2aa188d12c240ae2794b00ea0.zip", "parent_buildnumber": "39199", "got_revision": "66e8568f2fc06dd2aa188d12c240ae2794b00ea0", "parent_revision": "66e8568f2fc06dd2aa188d12c240ae2794b00ea0", "blamelist_real": ["blink-deps-roller@chromium.org", "brettw@chromium.org", "cjhopman@chromium.org", "dbeam@chromium.org", "hidehiko@chromium.org", "jamesr@chromium.org", "joth@chromium.org", "kelvinp@chromium.org", "kouhei@chromium.org", "ksakamoto@chromium.org", "mtomasz@chromium.org", "sashab@chromium.org", "skia-deps-roller@chromium.org", "tfarina@chromium.org", "wuchengli@chromium.org", "zsborbely.u-szeged@partner.samsung.com"], "got_webkit_revision_git": "721f3e2ce5a10cfb21d12f672bbcc2023d9a228d", "parent_slavename": "vm870-m1", "got_v8_revision_git": "26db57054e04a5b35e7ad88aecb3e05895491a5c", "project": "src", "repository": "https://chromium.googlesource.com/chromium/src", "parent_scheduler": "android", "parent_got_swarming_client_revision": "bcb3bc30328c38441d3f7656cb649b123803726c", "git_revision": "66e8568f2fc06dd2aa188d12c240ae2794b00ea0", "slavename": "chromeperf72", "got_revision_cp": "refs/heads/master@{#301052}", "blamelist": "blink-deps-roller@chromium.org,brettw@chromium.org,cjhopman@chromium.org,dbeam@chromium.org,hidehiko@chromium.org,jamesr@chromium.org,joth@chromium.org,kelvinp@chromium.org,kouhei@chromium.org,ksakamoto@chromium.org,mtomasz@chromium.org,sashab@chromium.org,skia-deps-roller@chromium.org,tfarina@chromium.org,wuchengli@chromium.org,zsborbely.u-szeged@partner.samsung.com", "branch": "master", "patchset": "", "issue": "", "revision": "66e8568f2fc06dd2aa188d12c240ae2794b00ea0", "workdir": "/b/build/slave/Android_Tests", "got_webkit_revision": "184325", "buildername": "Android Tests", "parent_try_job_key": "", "mastername": "chromium.linux", "parent_got_webkit_revision": "184325", "parent_builddir": "", "parent_branch": "master", "got_v8_revision_cp": "refs/heads/candidates@{#24827}", "primary_repo": "", "scheduler": "android_trigger_rel", "requester": "", "buildbotURL": "http://build.chromium.org/p/chromium.linux/", "parent_cr_revision": "66e8568f2fc06dd2aa188d12c240ae2794b00ea0", "rietveld": "", "parent_got_nacl_revision": "", "parent_buildername": "Android Builder", "got_v8_revision": "24827", "parent_got_revision": "66e8568f2fc06dd2aa188d12c240ae2794b00ea0", "got_webkit_revision_cp": "refs/heads/master@{#184325}", "buildnumber": 16413, "patch_url": "", "parent_git_number": "", "parentslavename": "vm870-m1", "root": ""}' -f ui -f unit -f mojo -f telemetry_perf_unittests -f chrome_proxy --cleanup --flakiness-server=test-results.appspot.com
Unknown tests ['mojo']

Please remove execution of the test from the buildbot configuration (recipe?) first, then reland this.

Original issue's description:
> Remove mojo test step from bb_device_steps.py
>
> This code is being developed and tested in the mojo repository.
>
> R=dpranke@chromium.org
> TBR=navabi@chromium.org
>
> Committed: https://crrev.com/7ec86e83523b60bab33f1739469ff0a0801c8eb4
> Cr-Commit-Position: refs/heads/master@{#301038}

TBR=dpranke@chromium.org,jbudorick@chromium.org,navabi@chromium.org,jamesr@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/646883003

Cr-Commit-Position: refs/heads/master@{#301067}