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

tools/telemetry/telemetry/core/backends/android_command_line_backend_unittest.py

Index: tools/telemetry/telemetry/core/backends/android_command_line_backend_unittest.py
diff --git a/tools/telemetry/telemetry/core/backends/android_command_line_backend_unittest.py b/tools/telemetry/telemetry/core/backends/android_command_line_backend_unittest.py
index 4e7b5294dfa655e237dd239bdaed50e919e701a9..b7ec6a935000e7a3c3d004e4a6320b57141529fe 100644
--- a/tools/telemetry/telemetry/core/backends/android_command_line_backend_unittest.py
+++ b/tools/telemetry/telemetry/core/backends/android_command_line_backend_unittest.py
@@ -2,10 +2,22 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import logging
 import unittest
 
+from telemetry import benchmark
+from telemetry.core.backends import adb_commands
 from telemetry.core.backends import android_command_line_backend
 
+class _MockBackendSettings(object):
+  pseudo_exec_name = 'chrome'
+
+  def __init__(self, path):
+    self._path = path
+
+  def GetCommandLineFile(self, _is_user_debug_build):
+    return self._path
+
 
 class AndroidCommandLineBackendTest(unittest.TestCase):
 
@@ -29,3 +41,43 @@ class AndroidCommandLineBackendTest(unittest.TestCase):
     expected_output = "key='valueA valueB'"
     self.assertEqual(expected_output,
                      android_command_line_backend._QuoteIfNeeded(string))
+
+  @benchmark.Enabled('android')
+  def testSetUpCommandLineFlagsCmdRestored(self):
+    """Test that a previous command line file is restored.
+
+    Requires a device connected to the host.
+    """
+    serial = adb_commands.GetAttachedDevices()[0]
+    cmd_file = '/data/local/tmp/test_cmd'
+    adb = adb_commands.AdbCommands(device=serial)
+    backend_settings = _MockBackendSettings('/data/local/tmp/test_cmd')
+    startup_args = ['--some', '--test', '--args']
+    device = adb.device()
+    device.WriteFile(cmd_file, 'chrome --args --to --save')
+    with android_command_line_backend.SetUpCommandLineFlags(
+        adb, backend_settings, startup_args):
+      self.assertEqual('chrome --some --test --args',
+                       device.ReadFile(cmd_file).strip())
+    self.assertEqual('chrome --args --to --save',
+                     device.ReadFile(cmd_file).strip())
+    device.RunShellCommand(['rm', '-f', cmd_file], check_return=True)
+
+  @benchmark.Enabled('android')
+  def testSetUpCommandLineFlagsCmdRemoved(self):
+    """Test that the command line file is removed if it did not exist before.
+
+    Requires a device connected to the host.
+    """
+    serial = adb_commands.GetAttachedDevices()[0]
+    cmd_file = '/data/local/tmp/test_cmd'
+    adb = adb_commands.AdbCommands(device=serial)
+    backend_settings = _MockBackendSettings('/data/local/tmp/test_cmd')
+    startup_args = ['--some', '--test', '--args']
+    device = adb.device()
+    device.RunShellCommand(['rm', '-f', cmd_file], check_return=True)
+    with android_command_line_backend.SetUpCommandLineFlags(
+        adb, backend_settings, startup_args):
+      self.assertEqual('chrome --some --test --args',
+                       device.ReadFile(cmd_file).strip())
+    self.assertFalse(device.FileExists(cmd_file))