A lack of adbd root permissions results in a variety of errors when running a modern Android emulator environment (sdk 26, android 7.0). $ adb shell ls /data/local ls: /data/local: Permission denied $ adb root $ adb shell ls /data/local tmp We already try to use 'adb root' in android_emulator_unittest.py, but it does not always work because we try to use it too early: [task 2017-12-14T04:42:01.803Z] 04:42:01 INFO - Running timeout 30 /builds/worker/workspace/build/android-sdk-linux/platform-tools/adb kill-server [task 2017-12-14T04:42:01.807Z] 04:42:01 INFO - stderr: * server not running * [task 2017-12-14T04:42:01.807Z] 04:42:01 INFO - Running timeout 30 /builds/worker/workspace/build/android-sdk-linux/platform-tools/adb root [task 2017-12-14T04:42:05.063Z] 04:42:05 INFO - * daemon not running. starting it now at tcp:5037 * [task 2017-12-14T04:42:05.063Z] 04:42:05 INFO - * daemon started successfully * [task 2017-12-14T04:42:05.063Z] 04:42:05 INFO - stderr: adb: unable to connect for root: no devices/emulators found

This fixes this issue on trial runs with Android 7 on an arm emulator. It doesn't break any existing jobs: https://treeherder.mozilla.org/#/jobs?repo=try&revision=963a48a15613549db8708914a40f67dd8438dcc2

Pushed by gbrown@mozilla.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/1a337abb11ee In android emulator tests, restart adbd after emulator has started; r=jmaher