Reland of Migrate DeviceUtils.ReadFile to adb_wrapper (try 3)

tools/telemetry/telemetry/core/forwarders/android_forwarder.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 re
 import socket
 import struct
 import subprocess
@@ skipping 213 matching lines @@
     if host_platform == 'linux':
       return subprocess.check_output(['ip', 'addr']).splitlines()
     if host_platform == 'mac':
       return subprocess.check_output(['ifconfig']).splitlines()
     raise NotImplementedError('Platform %s not supported!' % host_platform)
 
   def _FindHostRndisInterface(self):
     """Returns the name of the host-side network interface."""
     interface_list = self._EnumerateHostInterfaces()
     ether_address = self._device.ReadFile(
-        '%s/f_rndis/ethaddr' % self._RNDIS_DEVICE)[0]
+        '%s/f_rndis/ethaddr' % self._RNDIS_DEVICE).strip()
     interface_name = None
     for line in interface_list:
       if not line.startswith((' ', '\t')):
         interface_name = line.split(':')[-2].strip()
       elif ether_address in line:
         return interface_name
 
   def _WriteProtectedFile(self, file_path, contents):
     subprocess.check_call(
         ['/usr/bin/sudo', 'bash', '-c',
@@ skipping 70 matching lines @@
 }
 
 doit &
     """ % {'dev': self._RNDIS_DEVICE, 'functions': 'rndis,adb',
            'prefix': script_prefix}
     self._device.WriteFile('%s.sh' % script_prefix, script)
     # TODO(szym): run via su -c if necessary.
     self._device.RunShellCommand('rm %s.log' % script_prefix)
     self._device.RunShellCommand('. %s.sh' % script_prefix)
     self._WaitForDevice()
-    result = self._device.ReadFile('%s.log' % script_prefix)
+    result = self._device.ReadFile('%s.log' % script_prefix).splitlines()
     assert any('DONE' in line for line in result), 'RNDIS script did not run!'
 
   def _CheckEnableRndis(self, force):
     """Enables the RNDIS network interface, retrying if necessary.
     Args:
       force: Disable RNDIS first, even if it appears already enabled.
     Returns:
       device_iface: RNDIS interface name on the device
       host_iface: corresponding interface name on the host
     """
@@ skipping 186 matching lines @@
       device_iface, host_iface = self._CheckEnableRndis(force)
       self._ConfigureNetwork(device_iface, host_iface)
       self.OverrideRoutingPolicy()
       # Sometimes the first packet will wake up the connection.
       for _ in range(3):
         if self._TestConnectivity():
           return
       force = True
     self.RestoreRoutingPolicy()
     raise Exception('No connectivity, giving up.')