[Telemetry] Enable adb root on devices.

The perf bots aren't hitting this explicitly anywhere and provision devices
seems like the right place for it.

This method outputs a warning, but doesn't fail hard, if root cannot be enabled,
for instance on a user build.

BUG=366697
NOTRY=True

Review URL: https://codereview.chromium.org/255713007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266325 0039d316-1c4b-4281-b951-d872f2087c98

build/android/provision_devices.py

@@ -123,6 +123,7 @@ def ProvisionDevices(options):
     devices = android_commands.GetAttachedDevices()
   for device_serial in devices:
     device = device_utils.DeviceUtils(device_serial)
+    device.old_interface.EnableAdbRoot()
     install_output = GetCmdOutput(
       ['%s/build/android/adb_install_apk.py' % constants.DIR_SOURCE_ROOT,
        '--apk',