Revert of [Telemetry] Remove the logic of killing stray adb processes

telemetry/telemetry/internal/platform/android_device.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 import os
+import subprocess
 
 from telemetry.core import util
 from telemetry.internal.platform import cros_device
 from telemetry.internal.platform import device
 from telemetry.internal.platform.profiler import monsoon
 
 from devil.android import device_blacklist
 from devil.android import device_errors
 from devil.android import device_utils
 from devil.android.sdk import adb_wrapper
 
 
+def _KillStrayADBProcesses():
+  p = subprocess.Popen(['killall', 'adb'])
+  p.communicate()
+  if p.returncode:
+    logging.info('No adb process was killed')
+  else:
+    logging.info('Some adb process was killed')
+
+
+
 class AndroidDevice(device.Device):
   """ Class represents information for connecting to an android device.
 
   Attributes:
     device_id: the device's serial string created by adb to uniquely
       identify an emulator/device instance. This string can be found by running
       'adb devices' command
     enable_performance_mode: when this is set to True, android platform will be
     set to high performance mode after browser is started.
   """
@@ skipping 23 matching lines @@
           if d.IsOnline()]
 
 
 def GetDeviceSerials(blacklist):
   """Return the list of device serials of healthy devices.
 
   If a preferred device has been set with ANDROID_SERIAL, it will be first in
   the returned list. The arguments specify what devices to include in the list.
   """
 
-  device_serials = _ListSerialsOfHealthyOnlineDevices(blacklist)
+  try:
+    device_serials = _ListSerialsOfHealthyOnlineDevices(blacklist)
+  # Sometimes stray adb processes can interfere with using adb.
+  except device_errors.AdbCommandFailedError:
+    _KillStrayADBProcesses()
+    device_serials = _ListSerialsOfHealthyOnlineDevices(blacklist)
 
   # The monsoon provides power for the device, so for devices with no
   # real battery, we need to turn them on after the monsoon enables voltage
   # output to the device.
   if not device_serials:
     try:
       m = monsoon.Monsoon(wait=False)
       m.SetUsbPassthrough(1)
       m.SetVoltage(3.8)
       m.SetMaxCurrent(8)
@@ skipping 106 matching lines @@
       devices = AndroidDevice.GetAllConnectedDevices(blacklist)
   finally:
     if not devices and _HasValidAdb():
       try:
         adb_wrapper.AdbWrapper.KillServer()
       except device_errors.NoAdbError as e:
         logging.warning(
             'adb reported as present, but NoAdbError thrown: %s', str(e))
 
   return devices