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

tools/telemetry/telemetry/core/platform/android_platform_backend_unittest.py

 # Copyright 2013 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 unittest
 
 from telemetry import decorators
 from telemetry.core.platform import android_device
 from telemetry.core.platform import android_platform_backend
 from telemetry.unittest_util import system_stub
 
 
 class AndroidPlatformBackendTest(unittest.TestCase):
   def setUp(self):
     self._stubs = system_stub.Override(
         android_platform_backend,
         ['perf_control', 'thermal_throttle', 'adb_commands', 'certutils',
          'adb_install_cert'])
 
     # Skip _FixPossibleAdbInstability by setting psutil to None.
     self._actual_ps_util = android_platform_backend.psutil
     android_platform_backend.psutil = None
 
   def tearDown(self):
     self._stubs.Restore()
     android_platform_backend.psutil = self._actual_ps_util
 
   @decorators.Disabled('chromeos')
   def testGetCpuStats(self):
-    proc_stat_content = [
+    proc_stat_content = (
         '7702 (.android.chrome) S 167 167 0 0 -1 1077936448 '
         '3247 0 0 0 4 1 0 0 20 0 9 0 5603962 337379328 5867 '
         '4294967295 1074458624 1074463824 3197495984 3197494152 '
         '1074767676 0 4612 0 38136 4294967295 0 0 17 0 0 0 0 0 0 '
-        '1074470376 1074470912 1102155776']
+        '1074470376 1074470912 1102155776\n')
     self._stubs.adb_commands.adb_device.mock_content = proc_stat_content
     old_interface = self._stubs.adb_commands.adb_device.old_interface
     old_interface.can_access_protected_file_contents = True
     backend = android_platform_backend.AndroidPlatformBackend(
         android_device.AndroidDevice('12345'))
     cpu_stats = backend.GetCpuStats('7702')
     self.assertEquals(cpu_stats, {'CpuProcessTime': 0.05})
 
   @decorators.Disabled('chromeos')
   def testGetCpuStatsInvalidPID(self):
@@ skipping 30 matching lines @@
     backend = android_platform_backend.AndroidPlatformBackend(
         android_device.AndroidDevice('failure'))
     backend.InstallTestCa()
     self.assertFalse(backend.is_test_ca_installed)
 
   def testInstallTestCaSuccess(self):
     backend = android_platform_backend.AndroidPlatformBackend(
         android_device.AndroidDevice('success'))
     backend.InstallTestCa()
     self.assertTrue(backend.is_test_ca_installed)