diff --git a/android/gyp/create_device_library_links.py b/android/gyp/create_device_library_links.py
index 599642aa7..d5828f4c3 100755
--- a/android/gyp/create_device_library_links.py
+++ b/android/gyp/create_device_library_links.py
@@ -64,7 +64,7 @@ def TriggerSymlinkScript(options):
   mkdir_cmd = ('if [ ! -e %(dir)s ]; then mkdir -p %(dir)s; fi ' %
       { 'dir': device_dir })
   RunShellCommand(device, mkdir_cmd)
-  device.PushIfNeeded(options.script_host_path, options.script_device_path)
+  device.PushChangedFiles(options.script_host_path, options.script_device_path)
 
   trigger_cmd = (
       'APK_LIBRARIES_DIR=%(apk_libraries_dir)s; '
diff --git a/android/gyp/push_libraries.py b/android/gyp/push_libraries.py
index 21258efe6..efb9dfcc6 100755
--- a/android/gyp/push_libraries.py
+++ b/android/gyp/push_libraries.py
@@ -40,7 +40,7 @@ def DoPush(options):
       if needs_directory:
         device.RunShellCommand('mkdir -p ' + options.device_dir)
         needs_directory[:] = [] # = False
-      device.PushIfNeeded(host_path, device_path)
+      device.PushChangedFiles(host_path, device_path)
 
     record_path = '%s.%s.push.md5.stamp' % (host_path, serial_number)
     md5_check.CallAndRecordIfStale(
diff --git a/android/gyp/util/build_device.py b/android/gyp/util/build_device.py
index a5b0dd539..b153a157b 100644
--- a/android/gyp/util/build_device.py
+++ b/android/gyp/util/build_device.py
@@ -33,8 +33,8 @@ class BuildDevice(object):
   def RunShellCommand(self, *args, **kwargs):
     return self.device.RunShellCommand(*args, **kwargs)
 
-  def PushIfNeeded(self, *args, **kwargs):
-    return self.device.old_interface.PushIfNeeded(*args, **kwargs)
+  def PushChangedFiles(self, *args, **kwargs):
+    return self.device.PushChangedFiles(*args, **kwargs)
 
   def GetSerialNumber(self):
     return self.id
diff --git a/android/provision_devices.py b/android/provision_devices.py
index beb4106a9..82833de71 100755
--- a/android/provision_devices.py
+++ b/android/provision_devices.py
@@ -72,7 +72,7 @@ def PushAndLaunchAdbReboot(devices, target):
     print '  Pushing adb_reboot ...'
     adb_reboot = os.path.join(constants.DIR_SOURCE_ROOT,
                               'out/%s/adb_reboot' % target)
-    device.old_interface.PushIfNeeded(adb_reboot, '/data/local/tmp/')
+    device.PushChangedFiles(adb_reboot, '/data/local/tmp/')
     # Launch adb_reboot
     print '  Launching adb_reboot ...'
     device.old_interface.GetAndroidToolStatusAndOutput(
@@ -91,9 +91,9 @@ def _ConfigureLocalProperties(device, is_perf):
   if not is_perf:
     local_props.append('%s=all' % android_commands.JAVA_ASSERT_PROPERTY)
     local_props.append('debug.checkjni=1')
-  device.old_interface.SetProtectedFileContents(
+  device.WriteFile(
       constants.DEVICE_LOCAL_PROPERTIES_PATH,
-      '\n'.join(local_props))
+      '\n'.join(local_props), as_root=True)
   # Android will not respect the local props file if it is world writable.
   device.RunShellCommand(
       'chmod 644 %s' % constants.DEVICE_LOCAL_PROPERTIES_PATH,
@@ -114,8 +114,7 @@ def WipeDeviceData(device):
   Arguments:
     device: the device to wipe
   """
-  device_authorized = device.old_interface.FileExistsOnDevice(
-      constants.ADB_KEYS_FILE)
+  device_authorized = device.FileExists(constants.ADB_KEYS_FILE)
   if device_authorized:
     adb_keys = device.RunShellCommand('cat %s' % constants.ADB_KEYS_FILE,
                                       as_root=True)
diff --git a/android/pylib/android_commands.py b/android/pylib/android_commands.py
index df7e56f70..3d13f196a 100644
--- a/android/pylib/android_commands.py
+++ b/android/pylib/android_commands.py
@@ -1054,7 +1054,9 @@ class AndroidCommands(object):
     All pushed files can be removed by calling RemovePushedFiles().
     """
     MAX_INDIVIDUAL_PUSHES = 50
-    assert os.path.exists(host_path), 'Local path not found %s' % host_path
+    if not os.path.exists(host_path):
+      raise device_errors.CommandFailedError(
+          'Local path not found %s' % host_path, device=str(self))
 
     # See if the file on the host changed since the last push (if any) and
     # return early if it didn't. Note that this shortcut assumes that the tests
@@ -1110,8 +1112,6 @@ class AndroidCommands(object):
     # approximates the push time for each method.
     if len(changed_files) > MAX_INDIVIDUAL_PUSHES or diff_size > 0.5 * size:
       self._actual_push_size += size
-      if os.path.isdir(host_path):
-        self.RunShellCommand('mkdir -p %s' % device_path)
       Push(host_path, device_path)
     else:
       for f in changed_files:
@@ -1783,7 +1783,9 @@ class AndroidCommands(object):
       device_file: Absolute path to the file to retrieve from the device.
       host_file: Absolute path to the file to store on the host.
     """
-    assert self._adb.Pull(device_file, host_file)
+    if not self._adb.Pull(device_file, host_file):
+      raise device_errors.AdbCommandFailedError(
+          ['pull', device_file, host_file], 'Failed to pull file from device.')
     assert os.path.exists(host_file)
 
   def SetUtilWrapper(self, util_wrapper):
diff --git a/android/pylib/base/base_test_runner.py b/android/pylib/base/base_test_runner.py
index 3431c46d0..cfd0c6c75 100644
--- a/android/pylib/base/base_test_runner.py
+++ b/android/pylib/base/base_test_runner.py
@@ -51,7 +51,7 @@ class BaseTestRunner(object):
 
   def _PushTestServerPortInfoToDevice(self):
     """Pushes the latest port information to device."""
-    self.device.old_interface.SetFileContents(
+    self.device.WriteFile(
         self.device.GetExternalStoragePath() + '/' +
             NET_TEST_SERVER_PORT_INFO_FILE,
         '%d:%d' % (self.test_server_spawner_port, self.test_server_port))
diff --git a/android/pylib/device/device_utils.py b/android/pylib/device/device_utils.py
index c87ca5143..28d258f4d 100644
--- a/android/pylib/device/device_utils.py
+++ b/android/pylib/device/device_utils.py
@@ -435,6 +435,117 @@ class DeviceUtils(object):
     """
     self.old_interface.SendKeyEvent(keycode)
 
+  PUSH_CHANGED_FILES_DEFAULT_TIMEOUT = 10 * _DEFAULT_TIMEOUT
+  PUSH_CHANGED_FILES_DEFAULT_RETRIES = _DEFAULT_RETRIES
+
+  @decorators.WithTimeoutAndRetriesDefaults(
+      PUSH_CHANGED_FILES_DEFAULT_TIMEOUT,
+      PUSH_CHANGED_FILES_DEFAULT_RETRIES)
+  def PushChangedFiles(self, host_path, device_path, timeout=None,
+                       retries=None):
+    """Push files to the device, skipping files that don't need updating.
+
+    Args:
+      host_path: A string containing the absolute path to the file or directory
+                 on the host that should be minimally pushed to the device.
+      device_path: A string containing the absolute path of the destination on
+                   the device.
+      timeout: Same as for |IsOnline|.
+      retries: Same as for |IsOnline|.
+    """
+    self.old_interface.PushIfNeeded(host_path, device_path)
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def FileExists(self, device_path, timeout=None, retries=None):
+    """Checks whether the given file exists on the device.
+
+    Args:
+      device_path: A string containing the absolute path to the file on the
+                   device.
+      timeout: Same as for |IsOnline|.
+      retries: Same as for |IsOnline|.
+    Returns:
+      True if the file exists on the device, False otherwise.
+    """
+    return self._FileExistsImpl(device_path)
+
+  def _FileExistsImpl(self, device_path):
+    """Implementation of FileExists.
+
+    This is split from FileExists to allow other DeviceUtils methods to call
+    FileExists without spawning a new timeout thread.
+
+    Args:
+      device_path: Same as for |FileExists|.
+    Returns:
+      True if the file exists on the device, False otherwise.
+    """
+    return self.old_interface.FileExistsOnDevice(device_path)
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def PullFile(self, device_path, host_path, timeout=None, retries=None):
+    """Pull a file from the device.
+
+    Args:
+      device_path: A string containing the absolute path of the file to pull
+                   from the device.
+      host_path: A string containing the absolute path of the destination on
+                 the host.
+      timeout: Same as for |IsOnline|.
+      retries: Same as for |IsOnline|.
+    """
+    self.old_interface.PullFileFromDevice(device_path, host_path)
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def ReadFile(self, device_path, as_root=False, timeout=None, retries=None):
+    """Reads the contents of a file from the device.
+
+    Args:
+      device_path: A string containing the absolute path of the file to read
+                   from the device.
+      as_root: A boolean indicating whether the read should be executed with
+               root priveleges.
+      timeout: Same as for |IsOnline|.
+      retries: Same as for |IsOnline|.
+    Returns:
+      The contents of the file at |device_path| as a list of lines.
+    Raises:
+      CommandFailedError if the file can't be read.
+    """
+    # TODO(jbudorick) Evaluate whether we actually want to return a list of
+    # lines after the implementation switch.
+    if as_root:
+      if not self.old_interface.CanAccessProtectedFileContents():
+        raise device_errors.CommandFailedError(
+          'Cannot read from %s with root priveleges.' % device_path)
+      return self.old_interface.GetProtectedFileContents(device_path)
+    else:
+      return self.old_interface.GetFileContents(device_path)
+
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def WriteFile(self, device_path, contents, as_root=False, timeout=None,
+                retries=None):
+    """Writes |contents| to a file on the device.
+
+    Args:
+      device_path: A string containing the absolute path to the file to write
+                   on the device.
+      contents: A string containing the data to write to the device.
+      as_root: A boolean indicating whether the write should be executed with
+               root priveleges.
+      timeout: Same as for |IsOnline|.
+      retries: Same as for |IsOnline|.
+    Raises:
+      CommandFailedError if the file could not be written on the device.
+    """
+    if as_root:
+      if not self.old_interface.CanAccessProtectedFileContents():
+        raise device_errors.CommandFailedError(
+            'Cannot write to %s with root priveleges.' % device_path)
+      self.old_interface.SetProtectedFileContents(device_path, contents)
+    else:
+      self.old_interface.SetFileContents(device_path, contents)
+
   def __str__(self):
     """Returns the device serial."""
     return self.old_interface.GetDevice()
diff --git a/android/pylib/device/device_utils_test.py b/android/pylib/device/device_utils_test.py
index 4c60514da..d7ac6d7c4 100644
--- a/android/pylib/device/device_utils_test.py
+++ b/android/pylib/device/device_utils_test.py
@@ -10,7 +10,9 @@ Unit tests for the contents of device_utils.py (mostly DeviceUtils).
 # pylint: disable=W0212
 # pylint: disable=W0613
 
+import collections
 import os
+import re
 import signal
 import sys
 import unittest
@@ -64,8 +66,9 @@ class DeviceUtilsOldImplTest(unittest.TestCase):
 
   class AndroidCommandsCalls(object):
 
-    def __init__(self, test_case, cmd_ret):
+    def __init__(self, test_case, cmd_ret, comp):
       self._cmds = cmd_ret
+      self._comp = comp
       self._test_case = test_case
       self._total_received = 0
 
@@ -74,18 +77,20 @@ class DeviceUtilsOldImplTest(unittest.TestCase):
       atr_run_command.RunCommand.side_effect = lambda c, **kw: self._ret(c)
 
     def _ret(self, actual_cmd):
-      on_failure_fmt = ('\n'
-                        '  received command: %s\n'
-                        '  expected command: %s')
-      self._test_case.assertGreater(
-          len(self._cmds), self._total_received,
-          msg=on_failure_fmt % (actual_cmd, None))
-      expected_cmd, ret = self._cmds[self._total_received]
-      self._total_received += 1
-      self._test_case.assertEqual(
-          actual_cmd, expected_cmd,
-          msg=on_failure_fmt % (actual_cmd, expected_cmd))
-      return ret
+      if sys.exc_info()[0] is None:
+        on_failure_fmt = ('\n'
+                          '  received command: %s\n'
+                          '  expected command: %s')
+        self._test_case.assertGreater(
+            len(self._cmds), self._total_received,
+            msg=on_failure_fmt % (actual_cmd, None))
+        expected_cmd, ret = self._cmds[self._total_received]
+        self._total_received += 1
+        self._test_case.assertTrue(
+            self._comp(expected_cmd, actual_cmd),
+            msg=on_failure_fmt % (actual_cmd, expected_cmd))
+        return ret
+      return ''
 
     def __exit__(self, exc_type, _exc_val, exc_trace):
       if exc_type is None:
@@ -99,18 +104,21 @@ class DeviceUtilsOldImplTest(unittest.TestCase):
         for (expected_cmd, _r), (_n, actual_args, actual_kwargs) in zip(
             self._cmds, atr_run_command.RunCommand.mock_calls):
           self._test_case.assertEqual(1, len(actual_args), msg=on_failure)
-          self._test_case.assertEqual(expected_cmd, actual_args[0],
-                                      msg=on_failure)
+          self._test_case.assertTrue(self._comp(expected_cmd, actual_args[0]),
+                                     msg=on_failure)
           self._test_case.assertTrue('timeout_time' in actual_kwargs,
                                      msg=on_failure)
           self._test_case.assertTrue('retry_count' in actual_kwargs,
                                      msg=on_failure)
 
-  def assertOldImplCalls(self, cmd, ret):
-    return type(self).AndroidCommandsCalls(self, [(cmd, ret)])
+  def assertNoAdbCalls(self):
+    return type(self).AndroidCommandsCalls(self, [], str.__eq__)
 
-  def assertOldImplCallsSequence(self, cmd_ret):
-    return type(self).AndroidCommandsCalls(self, cmd_ret)
+  def assertOldImplCalls(self, cmd, ret, comp=str.__eq__):
+    return type(self).AndroidCommandsCalls(self, [(cmd, ret)], comp)
+
+  def assertOldImplCallsSequence(self, cmd_ret, comp=str.__eq__):
+    return type(self).AndroidCommandsCalls(self, cmd_ret, comp)
 
   def setUp(self):
     self.device = device_utils.DeviceUtils(
@@ -717,6 +725,468 @@ class DeviceUtilsOldImplTest(unittest.TestCase):
         ''):
       self.device.SendKeyEvent(66)
 
+  def testPushChangedFiles_noHostPath(self):
+    with mock.patch('os.path.exists', return_value=False):
+      with self.assertRaises(device_errors.CommandFailedError):
+        self.device.PushChangedFiles('/test/host/path', '/test/device/path')
+
+  def testPushChangedFiles_file_noChange(self):
+    self.device.old_interface._push_if_needed_cache = {}
+
+    host_file_path = '/test/host/path'
+    device_file_path = '/test/device/path'
+
+    mock_file_info = {
+      '/test/host/path': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 100,
+      },
+    }
+
+    os_path_exists = mock.Mock()
+    os_path_exists.side_effect = lambda f: mock_file_info[f]['os.path.exists']
+
+    os_path_isdir = mock.Mock()
+    os_path_isdir.side_effect = lambda f: mock_file_info[f]['os.path.isdir']
+
+    os_path_getsize = mock.Mock()
+    os_path_getsize.side_effect = lambda f: mock_file_info[f]['os.path.getsize']
+
+    self.device.old_interface.GetFilesChanged = mock.Mock(return_value=[])
+
+    with mock.patch('os.path.exists', new=os_path_exists), (
+         mock.patch('os.path.isdir', new=os_path_isdir)), (
+         mock.patch('os.path.getsize', new=os_path_getsize)):
+      # GetFilesChanged is mocked, so its adb calls are omitted.
+      with self.assertNoAdbCalls():
+        self.device.PushChangedFiles(host_file_path, device_file_path)
+
+  @staticmethod
+  def createMockOSStatResult(
+      st_mode=None, st_ino=None, st_dev=None, st_nlink=None, st_uid=None,
+      st_gid=None, st_size=None, st_atime=None, st_mtime=None, st_ctime=None):
+    MockOSStatResult = collections.namedtuple('MockOSStatResult', [
+        'st_mode', 'st_ino', 'st_dev', 'st_nlink', 'st_uid', 'st_gid',
+        'st_size', 'st_atime', 'st_mtime', 'st_ctime'])
+    return MockOSStatResult(st_mode, st_ino, st_dev, st_nlink, st_uid, st_gid,
+                            st_size, st_atime, st_mtime, st_ctime)
+
+  def testPushChangedFiles_file_changed(self):
+    self.device.old_interface._push_if_needed_cache = {}
+
+    host_file_path = '/test/host/path'
+    device_file_path = '/test/device/path'
+
+    mock_file_info = {
+      '/test/host/path': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 100,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000000)
+      },
+    }
+
+    os_path_exists = mock.Mock()
+    os_path_exists.side_effect = lambda f: mock_file_info[f]['os.path.exists']
+
+    os_path_isdir = mock.Mock()
+    os_path_isdir.side_effect = lambda f: mock_file_info[f]['os.path.isdir']
+
+    os_path_getsize = mock.Mock()
+    os_path_getsize.side_effect = lambda f: mock_file_info[f]['os.path.getsize']
+
+    os_stat = mock.Mock()
+    os_stat.side_effect = lambda f: mock_file_info[f]['os.stat']
+
+    self.device.old_interface.GetFilesChanged = mock.Mock(
+        return_value=[('/test/host/path', '/test/device/path')])
+
+    with mock.patch('os.path.exists', new=os_path_exists), (
+         mock.patch('os.path.isdir', new=os_path_isdir)), (
+         mock.patch('os.path.getsize', new=os_path_getsize)), (
+         mock.patch('os.stat', new=os_stat)):
+      with self.assertOldImplCalls('adb -s 0123456789abcdef push '
+          '/test/host/path /test/device/path', '100 B/s (100 B in 1.000s)\r\n'):
+        self.device.PushChangedFiles(host_file_path, device_file_path)
+
+  def testPushChangedFiles_directory_nothingChanged(self):
+    self.device.old_interface._push_if_needed_cache = {}
+
+    host_file_path = '/test/host/path'
+    device_file_path = '/test/device/path'
+
+    mock_file_info = {
+      '/test/host/path': {
+        'os.path.exists': True,
+        'os.path.isdir': True,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000000)
+      },
+      '/test/host/path/file1': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 251,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000001)
+      },
+      '/test/host/path/file2': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 252,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000002)
+      },
+    }
+
+    os_path_exists = mock.Mock()
+    os_path_exists.side_effect = lambda f: mock_file_info[f]['os.path.exists']
+
+    os_path_isdir = mock.Mock()
+    os_path_isdir.side_effect = lambda f: mock_file_info[f]['os.path.isdir']
+
+    os_path_getsize = mock.Mock()
+    os_path_getsize.side_effect = lambda f: mock_file_info[f]['os.path.getsize']
+
+    os_stat = mock.Mock()
+    os_stat.side_effect = lambda f: mock_file_info[f]['os.stat']
+
+    self.device.old_interface.GetFilesChanged = mock.Mock(return_value=[])
+
+    with mock.patch('os.path.exists', new=os_path_exists), (
+         mock.patch('os.path.isdir', new=os_path_isdir)), (
+         mock.patch('os.path.getsize', new=os_path_getsize)), (
+         mock.patch('os.stat', new=os_stat)):
+      with self.assertOldImplCallsSequence([
+          ("adb -s 0123456789abcdef shell 'mkdir -p \"/test/device/path\"'",
+           '')]):
+        self.device.PushChangedFiles(host_file_path, device_file_path)
+
+  def testPushChangedFiles_directory_somethingChanged(self):
+    self.device.old_interface._push_if_needed_cache = {}
+
+    host_file_path = '/test/host/path'
+    device_file_path = '/test/device/path'
+
+    mock_file_info = {
+      '/test/host/path': {
+        'os.path.exists': True,
+        'os.path.isdir': True,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000000),
+        'os.walk': [('/test/host/path', [], ['file1', 'file2'])]
+      },
+      '/test/host/path/file1': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000001)
+      },
+      '/test/host/path/file2': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000002)
+      },
+    }
+
+    os_path_exists = mock.Mock()
+    os_path_exists.side_effect = lambda f: mock_file_info[f]['os.path.exists']
+
+    os_path_isdir = mock.Mock()
+    os_path_isdir.side_effect = lambda f: mock_file_info[f]['os.path.isdir']
+
+    os_path_getsize = mock.Mock()
+    os_path_getsize.side_effect = lambda f: mock_file_info[f]['os.path.getsize']
+
+    os_stat = mock.Mock()
+    os_stat.side_effect = lambda f: mock_file_info[f]['os.stat']
+
+    os_walk = mock.Mock()
+    os_walk.side_effect = lambda f: mock_file_info[f]['os.walk']
+
+    self.device.old_interface.GetFilesChanged = mock.Mock(
+        return_value=[('/test/host/path/file1', '/test/device/path/file1')])
+
+    with mock.patch('os.path.exists', new=os_path_exists), (
+         mock.patch('os.path.isdir', new=os_path_isdir)), (
+         mock.patch('os.path.getsize', new=os_path_getsize)), (
+         mock.patch('os.stat', new=os_stat)), (
+         mock.patch('os.walk', new=os_walk)):
+      with self.assertOldImplCallsSequence([
+          ("adb -s 0123456789abcdef shell 'mkdir -p \"/test/device/path\"'",
+           ''),
+          ('adb -s 0123456789abcdef push '
+              '/test/host/path/file1 /test/device/path/file1',
+           '256 B/s (256 B in 1.000s)\r\n')]):
+        self.device.PushChangedFiles(host_file_path, device_file_path)
+
+  def testPushChangedFiles_directory_everythingChanged(self):
+    self.device.old_interface._push_if_needed_cache = {}
+
+    host_file_path = '/test/host/path'
+    device_file_path = '/test/device/path'
+
+    mock_file_info = {
+      '/test/host/path': {
+        'os.path.exists': True,
+        'os.path.isdir': True,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000000)
+      },
+      '/test/host/path/file1': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000001)
+      },
+      '/test/host/path/file2': {
+        'os.path.exists': True,
+        'os.path.isdir': False,
+        'os.path.getsize': 256,
+        'os.stat': self.createMockOSStatResult(st_mtime=1000000002)
+      },
+    }
+
+    os_path_exists = mock.Mock()
+    os_path_exists.side_effect = lambda f: mock_file_info[f]['os.path.exists']
+
+    os_path_isdir = mock.Mock()
+    os_path_isdir.side_effect = lambda f: mock_file_info[f]['os.path.isdir']
+
+    os_path_getsize = mock.Mock()
+    os_path_getsize.side_effect = lambda f: mock_file_info[f]['os.path.getsize']
+
+    os_stat = mock.Mock()
+    os_stat.side_effect = lambda f: mock_file_info[f]['os.stat']
+
+    self.device.old_interface.GetFilesChanged = mock.Mock(
+        return_value=[('/test/host/path/file1', '/test/device/path/file1'),
+                      ('/test/host/path/file2', '/test/device/path/file2')])
+
+    with mock.patch('os.path.exists', new=os_path_exists), (
+         mock.patch('os.path.isdir', new=os_path_isdir)), (
+         mock.patch('os.path.getsize', new=os_path_getsize)), (
+         mock.patch('os.stat', new=os_stat)):
+      with self.assertOldImplCallsSequence([
+          ("adb -s 0123456789abcdef shell 'mkdir -p \"/test/device/path\"'",
+           ''),
+          ('adb -s 0123456789abcdef push /test/host/path /test/device/path',
+           '768 B/s (768 B in 1.000s)\r\n')]):
+        self.device.PushChangedFiles(host_file_path, device_file_path)
+
+  def testFileExists_usingTest_fileExists(self):
+    with self.assertOldImplCalls(
+        "adb -s 0123456789abcdef shell "
+            "'test -e \"/data/app/test.file.exists\"; echo $?'",
+        '0\r\n'):
+      self.assertTrue(self.device.FileExists('/data/app/test.file.exists'))
+
+  def testFileExists_usingTest_fileDoesntExist(self):
+    with self.assertOldImplCalls(
+        "adb -s 0123456789abcdef shell "
+            "'test -e \"/data/app/test.file.does.not.exist\"; echo $?'",
+        '1\r\n'):
+      self.assertFalse(self.device.FileExists(
+          '/data/app/test.file.does.not.exist'))
+
+  def testFileExists_usingLs_fileExists(self):
+    with self.assertOldImplCallsSequence([
+        ("adb -s 0123456789abcdef shell "
+            "'test -e \"/data/app/test.file.exists\"; echo $?'",
+         'test: not found\r\n'),
+        ("adb -s 0123456789abcdef shell "
+            "'ls \"/data/app/test.file.exists\" >/dev/null 2>&1; echo $?'",
+         '0\r\n')]):
+      self.assertTrue(self.device.FileExists('/data/app/test.file.exists'))
+
+  def testFileExists_usingLs_fileDoesntExist(self):
+    with self.assertOldImplCallsSequence([
+        ("adb -s 0123456789abcdef shell "
+            "'test -e \"/data/app/test.file.does.not.exist\"; echo $?'",
+         'test: not found\r\n'),
+        ("adb -s 0123456789abcdef shell "
+            "'ls \"/data/app/test.file.does.not.exist\" "
+            ">/dev/null 2>&1; echo $?'",
+         '1\r\n')]):
+      self.assertFalse(self.device.FileExists(
+          '/data/app/test.file.does.not.exist'))
+
+  def testPullFile_existsOnDevice(self):
+    with mock.patch('os.path.exists', return_value=True):
+      with self.assertOldImplCallsSequence([
+          ('adb -s 0123456789abcdef shell '
+              'ls /data/app/test.file.exists',
+           '/data/app/test.file.exists'),
+          ('adb -s 0123456789abcdef pull '
+              '/data/app/test.file.exists /test/file/host/path',
+           '100 B/s (100 bytes in 1.000s)\r\n')]):
+        self.device.PullFile('/data/app/test.file.exists',
+                             '/test/file/host/path')
+
+  def testPullFile_doesntExistOnDevice(self):
+    with mock.patch('os.path.exists', return_value=True):
+      with self.assertOldImplCalls(
+          'adb -s 0123456789abcdef shell '
+              'ls /data/app/test.file.does.not.exist',
+          '/data/app/test.file.does.not.exist: No such file or directory\r\n'):
+        with self.assertRaises(device_errors.CommandFailedError):
+          self.device.PullFile('/data/app/test.file.does.not.exist',
+                               '/test/file/host/path')
+
+  def testReadFile_exists(self):
+    with self.assertOldImplCallsSequence([
+        ("adb -s 0123456789abcdef shell "
+            "'cat \"/read/this/test/file\" 2>/dev/null'",
+         'this is a test file')]):
+      self.assertEqual(['this is a test file'],
+                       self.device.ReadFile('/read/this/test/file'))
+
+  def testReadFile_doesNotExist(self):
+    with self.assertOldImplCalls(
+        "adb -s 0123456789abcdef shell "
+            "'cat \"/this/file/does.not.exist\" 2>/dev/null'",
+         ''):
+      self.device.ReadFile('/this/file/does.not.exist')
+
+  def testReadFile_asRoot_withRoot(self):
+    self.device.old_interface._privileged_command_runner = (
+        self.device.old_interface.RunShellCommand)
+    self.device.old_interface._protected_file_access_method_initialized = True
+    with self.assertOldImplCallsSequence([
+        ("adb -s 0123456789abcdef shell "
+            "'cat \"/this/file/must.be.read.by.root\" 2> /dev/null'",
+         'this is a test file\nread by root')]):
+      self.assertEqual(
+          ['this is a test file', 'read by root'],
+          self.device.ReadFile('/this/file/must.be.read.by.root',
+                               as_root=True))
+
+  def testReadFile_asRoot_withSu(self):
+    self.device.old_interface._privileged_command_runner = (
+        self.device.old_interface.RunShellCommandWithSU)
+    self.device.old_interface._protected_file_access_method_initialized = True
+    with self.assertOldImplCallsSequence([
+        ("adb -s 0123456789abcdef shell "
+            "'su -c cat \"/this/file/can.be.read.with.su\" 2> /dev/null'",
+         'this is a test file\nread with su')]):
+      self.assertEqual(
+          ['this is a test file', 'read with su'],
+          self.device.ReadFile('/this/file/can.be.read.with.su',
+                               as_root=True))
+
+  def testReadFile_asRoot_rejected(self):
+    self.device.old_interface._privileged_command_runner = None
+    self.device.old_interface._protected_file_access_method_initialized = True
+    with self.assertRaises(device_errors.CommandFailedError):
+      self.device.ReadFile('/this/file/cannot.be.read.by.user',
+                           as_root=True)
+
+  def testWriteFile_basic(self):
+    mock_file = mock.MagicMock(spec=file)
+    mock_file.name = '/tmp/file/to.be.pushed'
+    mock_file.__enter__.return_value = mock_file
+    with mock.patch('tempfile.NamedTemporaryFile',
+                    return_value=mock_file):
+      with self.assertOldImplCalls(
+          'adb -s 0123456789abcdef push '
+              '/tmp/file/to.be.pushed /test/file/written.to.device',
+          '100 B/s (100 bytes in 1.000s)\r\n'):
+        self.device.WriteFile('/test/file/written.to.device',
+                              'new test file contents')
+    mock_file.write.assert_called_once_with('new test file contents')
+
+  def testWriteFile_asRoot_withRoot(self):
+    self.device.old_interface._external_storage = '/fake/storage/path'
+    self.device.old_interface._privileged_command_runner = (
+        self.device.old_interface.RunShellCommand)
+    self.device.old_interface._protected_file_access_method_initialized = True
+
+    mock_file = mock.MagicMock(spec=file)
+    mock_file.name = '/tmp/file/to.be.pushed'
+    mock_file.__enter__.return_value = mock_file
+    with mock.patch('tempfile.NamedTemporaryFile',
+                    return_value=mock_file):
+      with self.assertOldImplCallsSequence(
+          cmd_ret=[
+              # Create temporary contents file
+              (r"adb -s 0123456789abcdef shell "
+                  "'test -e \"/fake/storage/path/temp_file-\d+-\d+\"; "
+                  "echo \$\?'",
+               '1\r\n'),
+              # Create temporary script file
+              (r"adb -s 0123456789abcdef shell "
+                  "'test -e \"/fake/storage/path/temp_file-\d+-\d+\.sh\"; "
+                  "echo \$\?'",
+               '1\r\n'),
+              # Set contents file
+              (r'adb -s 0123456789abcdef push /tmp/file/to\.be\.pushed '
+                  '/fake/storage/path/temp_file-\d+\d+',
+               '100 B/s (100 bytes in 1.000s)\r\n'),
+              # Set script file
+              (r'adb -s 0123456789abcdef push /tmp/file/to\.be\.pushed '
+                  '/fake/storage/path/temp_file-\d+\d+',
+               '100 B/s (100 bytes in 1.000s)\r\n'),
+              # Call script
+              (r"adb -s 0123456789abcdef shell "
+                  "'sh /fake/storage/path/temp_file-\d+-\d+\.sh'", ''),
+              # Remove device temporaries
+              (r"adb -s 0123456789abcdef shell "
+                  "'rm /fake/storage/path/temp_file-\d+-\d+\.sh'", ''),
+              (r"adb -s 0123456789abcdef shell "
+                  "'rm /fake/storage/path/temp_file-\d+-\d+'", '')],
+          comp=re.match):
+        self.device.WriteFile('/test/file/written.to.device',
+                              'new test file contents', as_root=True)
+
+  def testWriteFile_asRoot_withSu(self):
+    self.device.old_interface._external_storage = '/fake/storage/path'
+    self.device.old_interface._privileged_command_runner = (
+        self.device.old_interface.RunShellCommandWithSU)
+    self.device.old_interface._protected_file_access_method_initialized = True
+
+    mock_file = mock.MagicMock(spec=file)
+    mock_file.name = '/tmp/file/to.be.pushed'
+    mock_file.__enter__.return_value = mock_file
+    with mock.patch('tempfile.NamedTemporaryFile',
+                    return_value=mock_file):
+      with self.assertOldImplCallsSequence(
+          cmd_ret=[
+              # Create temporary contents file
+              (r"adb -s 0123456789abcdef shell "
+                  "'test -e \"/fake/storage/path/temp_file-\d+-\d+\"; "
+                  "echo \$\?'",
+               '1\r\n'),
+              # Create temporary script file
+              (r"adb -s 0123456789abcdef shell "
+                  "'test -e \"/fake/storage/path/temp_file-\d+-\d+\.sh\"; "
+                  "echo \$\?'",
+               '1\r\n'),
+              # Set contents file
+              (r'adb -s 0123456789abcdef push /tmp/file/to\.be\.pushed '
+                  '/fake/storage/path/temp_file-\d+\d+',
+               '100 B/s (100 bytes in 1.000s)\r\n'),
+              # Set script file
+              (r'adb -s 0123456789abcdef push /tmp/file/to\.be\.pushed '
+                  '/fake/storage/path/temp_file-\d+\d+',
+               '100 B/s (100 bytes in 1.000s)\r\n'),
+              # Call script
+              (r"adb -s 0123456789abcdef shell "
+                  "'su -c sh /fake/storage/path/temp_file-\d+-\d+\.sh'", ''),
+              # Remove device temporaries
+              (r"adb -s 0123456789abcdef shell "
+                  "'rm /fake/storage/path/temp_file-\d+-\d+\.sh'", ''),
+              (r"adb -s 0123456789abcdef shell "
+                  "'rm /fake/storage/path/temp_file-\d+-\d+'", '')],
+          comp=re.match):
+        self.device.WriteFile('/test/file/written.to.device',
+                              'new test file contents', as_root=True)
+
+  def testWriteFile_asRoot_rejected(self):
+    self.device.old_interface._privileged_command_runner = None
+    self.device.old_interface._protected_file_access_method_initialized = True
+    with self.assertRaises(device_errors.CommandFailedError):
+      self.device.WriteFile('/test/file/no.permissions.to.write',
+                            'new test file contents', as_root=True)
+
 
 if __name__ == '__main__':
   unittest.main(verbosity=2)
diff --git a/android/pylib/flag_changer.py b/android/pylib/flag_changer.py
index c1ce16a5e..c0bcadbe3 100644
--- a/android/pylib/flag_changer.py
+++ b/android/pylib/flag_changer.py
@@ -32,8 +32,7 @@ class FlagChanger(object):
     self._cmdline_file = cmdline_file
 
     # Save the original flags.
-    self._orig_line = self._device.old_interface.GetFileContents(
-        self._cmdline_file)
+    self._orig_line = self._device.ReadFile(self._cmdline_file)
     if self._orig_line:
       self._orig_line = self._orig_line[0].strip()
 
@@ -102,23 +101,16 @@ class FlagChanger(object):
       # The first command line argument doesn't matter as we are not actually
       # launching the chrome executable using this command line.
       cmd_line = ' '.join(['_'] + self._current_flags)
-      if use_root:
-        self._device.old_interface.SetProtectedFileContents(
-            self._cmdline_file, cmd_line)
-        file_contents = self._device.old_interface.GetProtectedFileContents(
-            self._cmdline_file)
-      else:
-        self._device.old_interface.SetFileContents(self._cmdline_file, cmd_line)
-        file_contents = self._device.old_interface.GetFileContents(
-            self._cmdline_file)
+      self._device.WriteFile(
+          self._cmdline_file, cmd_line, as_root=use_root)
+      file_contents = self._device.ReadFile(
+          self._cmdline_file, as_root=use_root)
       assert len(file_contents) == 1 and file_contents[0] == cmd_line, (
           'Failed to set the command line file at %s' % self._cmdline_file)
     else:
       self._device.RunShellCommand('rm ' + self._cmdline_file,
                                    as_root=use_root)
-      assert (
-          not self._device.old_interface.FileExistsOnDevice(
-              self._cmdline_file)), (
+      assert not self._device.FileExists(self._cmdline_file), (
           'Failed to remove the command line file at %s' % self._cmdline_file)
 
   @staticmethod
diff --git a/android/pylib/forwarder.py b/android/pylib/forwarder.py
index f0ddb2e5a..ad22838d8 100644
--- a/android/pylib/forwarder.py
+++ b/android/pylib/forwarder.py
@@ -290,7 +290,7 @@ class Forwarder(object):
     if device_serial in self._initialized_devices:
       return
     Forwarder._KillDeviceLocked(device, tool)
-    device.old_interface.PushIfNeeded(
+    device.PushChangedFiles(
         self._device_forwarder_path_on_host,
         Forwarder._DEVICE_FORWARDER_FOLDER)
     cmd = '%s %s' % (tool.GetUtilWrapper(), Forwarder._DEVICE_FORWARDER_PATH)
@@ -328,8 +328,7 @@ class Forwarder(object):
             forwarder (see valgrind_tools.py).
     """
     logging.info('Killing device_forwarder.')
-    if not device.old_interface.FileExistsOnDevice(
-        Forwarder._DEVICE_FORWARDER_PATH):
+    if not device.FileExists(Forwarder._DEVICE_FORWARDER_PATH):
       return
 
     cmd = '%s %s --kill-server' % (tool.GetUtilWrapper(),
diff --git a/android/pylib/gtest/test_package_apk.py b/android/pylib/gtest/test_package_apk.py
index 6374f637f..429cd2b07 100644
--- a/android/pylib/gtest/test_package_apk.py
+++ b/android/pylib/gtest/test_package_apk.py
@@ -44,7 +44,7 @@ class TestPackageApk(TestPackage):
     # GTest expects argv[0] to be the executable path.
     command_line_file.write(self.suite_name + ' ' + options)
     command_line_file.flush()
-    device.old_interface.PushIfNeeded(
+    device.PushChangedFiles(
         command_line_file.name,
         self._package_info.cmdline_file)
 
@@ -60,7 +60,7 @@ class TestPackageApk(TestPackage):
 
   def _WatchFifo(self, device, timeout, logfile=None):
     for i in range(10):
-      if device.old_interface.FileExistsOnDevice(self._GetFifo()):
+      if device.FileExists(self._GetFifo()):
         logging.info('Fifo created.')
         break
       time.sleep(i)
diff --git a/android/pylib/gtest/test_package_exe.py b/android/pylib/gtest/test_package_exe.py
index a7f603073..9714c4208 100644
--- a/android/pylib/gtest/test_package_exe.py
+++ b/android/pylib/gtest/test_package_exe.py
@@ -37,7 +37,7 @@ class TestPackageExecutable(TestPackage):
     ret_code = 1  # Assume failure if we can't find it
     ret_code_file = tempfile.NamedTemporaryFile()
     try:
-      if not device.old_interface.Adb().Pull(
+      if not device.PullFile(
           constants.TEST_EXECUTABLE_DIR + '/' +
           TestPackageExecutable._TEST_RUNNER_RET_VAL_FILE,
           ret_code_file.name):
@@ -105,7 +105,7 @@ class TestPackageExecutable(TestPackage):
                           TestPackageExecutable._TEST_RUNNER_RET_VAL_FILE))
     sh_script_file.flush()
     cmd_helper.RunCmd(['chmod', '+x', sh_script_file.name])
-    device.old_interface.PushIfNeeded(
+    device.PushChangedFiles(
         sh_script_file.name,
         constants.TEST_EXECUTABLE_DIR + '/chrome_test_runner.sh')
     logging.info('Conents of the test runner script: ')
@@ -148,4 +148,4 @@ class TestPackageExecutable(TestPackage):
              self.suite_name + '_stripped'))
 
     test_binary = constants.TEST_EXECUTABLE_DIR + '/' + self.suite_name
-    device.old_interface.PushIfNeeded(target_name, test_binary)
+    device.PushChangedFiles(target_name, test_binary)
diff --git a/android/pylib/gtest/test_runner.py b/android/pylib/gtest/test_runner.py
index cea799249..c9a60449c 100644
--- a/android/pylib/gtest/test_runner.py
+++ b/android/pylib/gtest/test_runner.py
@@ -71,7 +71,7 @@ class TestRunner(base_test_runner.BaseTestRunner):
       else:
         device_dir = self.device.GetExternalStoragePath()
       for p in os.listdir(constants.ISOLATE_DEPS_DIR):
-        self.device.old_interface.PushIfNeeded(
+        self.device.PushChangedFiles(
             os.path.join(constants.ISOLATE_DEPS_DIR, p),
             os.path.join(device_dir, p))
 
diff --git a/android/pylib/instrumentation/test_runner.py b/android/pylib/instrumentation/test_runner.py
index 050985f36..7359c1a5f 100644
--- a/android/pylib/instrumentation/test_runner.py
+++ b/android/pylib/instrumentation/test_runner.py
@@ -106,7 +106,7 @@ class TestRunner(base_test_runner.BaseTestRunner):
       # Make sure SD card is ready.
       self.device.WaitUntilFullyBooted(timeout=20)
       for p in test_data:
-        self.device.old_interface.PushIfNeeded(
+        self.device.PushChangedFiles(
             os.path.join(constants.DIR_SOURCE_ROOT, p),
             os.path.join(self.device.GetExternalStoragePath(), p))
 
@@ -118,7 +118,7 @@ class TestRunner(base_test_runner.BaseTestRunner):
       host_src = dst_src[1]
       host_test_files_path = '%s/%s' % (constants.DIR_SOURCE_ROOT, host_src)
       if os.path.exists(host_test_files_path):
-        self.device.old_interface.PushIfNeeded(
+        self.device.PushChangedFiles(
             host_test_files_path,
             '%s/%s/%s' % (
                 self.device.GetExternalStoragePath(),
@@ -235,7 +235,7 @@ class TestRunner(base_test_runner.BaseTestRunner):
     self.TearDownPerfMonitoring(test)
 
     if self.coverage_dir:
-      self.device.old_interface.Adb().Pull(
+      self.device.PullFile(
           self.coverage_device_file, self.coverage_host_file)
       self.device.RunShellCommand(
           'rm -f %s' % self.coverage_device_file)
@@ -266,8 +266,9 @@ class TestRunner(base_test_runner.BaseTestRunner):
 
       # Obtain the relevant perf data.  The data is dumped to a
       # JSON formatted file.
-      json_string = self.device.old_interface.GetProtectedFileContents(
-          '/data/data/com.google.android.apps.chrome/files/PerfTestData.txt')
+      json_string = self.device.ReadFile(
+          '/data/data/com.google.android.apps.chrome/files/PerfTestData.txt',
+          as_root=True)
 
       if json_string:
         json_string = '\n'.join(json_string)
diff --git a/android/pylib/perf/cache_control.py b/android/pylib/perf/cache_control.py
index a065dcbb7..8065cf9ad 100644
--- a/android/pylib/perf/cache_control.py
+++ b/android/pylib/perf/cache_control.py
@@ -17,6 +17,5 @@ class CacheControl(object):
   def DropRamCaches(self):
     """Drops the filesystem ram caches for performance testing."""
     self._device.RunShellCommand('sync', as_root=True)
-    self._device.old_interface.SetProtectedFileContents(
-        CacheControl._DROP_CACHES, '3')
+    self._device.WriteFile(CacheControl._DROP_CACHES, '3', as_root=True)
 
diff --git a/android/pylib/perf/perf_control.py b/android/pylib/perf/perf_control.py
index 0b32dd808..03c20bdc6 100644
--- a/android/pylib/perf/perf_control.py
+++ b/android/pylib/perf/perf_control.py
@@ -25,8 +25,7 @@ class PerfControl(object):
     self._num_cpu_cores = len(cpu_files)
     assert self._num_cpu_cores > 0, 'Failed to detect CPUs.'
     logging.info('Number of CPUs: %d', self._num_cpu_cores)
-    self._have_mpdecision = self._device.old_interface.FileExistsOnDevice(
-        '/system/bin/mpdecision')
+    self._have_mpdecision = self._device.FileExists('/system/bin/mpdecision')
 
   def SetHighPerfMode(self):
     # TODO(epenner): Enable on all devices (http://crbug.com/383566)
@@ -61,16 +60,15 @@ class PerfControl(object):
   def _SetScalingGovernorInternal(self, value):
     for cpu in range(self._num_cpu_cores):
       scaling_governor_file = PerfControl._SCALING_GOVERNOR_FMT % cpu
-      if self._device.old_interface.FileExistsOnDevice(scaling_governor_file):
+      if self._device.FileExists(scaling_governor_file):
         logging.info('Writing scaling governor mode \'%s\' -> %s',
                      value, scaling_governor_file)
-        self._device.old_interface.SetProtectedFileContents(
-            scaling_governor_file, value)
+        self._device.WriteFile(scaling_governor_file, value, as_root=True)
 
   def _AllCpusAreOnline(self):
     for cpu in range(self._num_cpu_cores):
       online_path = PerfControl._CPU_ONLINE_FMT % cpu
-      if self._device.old_interface.GetFileContents(online_path)[0] == '0':
+      if self._device.ReadFile(online_path)[0] == '0':
         return False
     return True
 
@@ -100,5 +98,4 @@ class PerfControl(object):
 
     for cpu in range(self._num_cpu_cores):
       online_path = PerfControl._CPU_ONLINE_FMT % cpu
-      self._device.old_interface.SetProtectedFileContents(
-          online_path, '1')
+      self._device.WriteFile(online_path, '1', as_root=True)
diff --git a/android/pylib/perf/perf_control_unittest.py b/android/pylib/perf/perf_control_unittest.py
index 9333dbce8..aa31f68d0 100644
--- a/android/pylib/perf/perf_control_unittest.py
+++ b/android/pylib/perf/perf_control_unittest.py
@@ -30,10 +30,10 @@ class TestPerfControl(unittest.TestCase):
       for cpu in range(perf._num_cpu_cores):
         path = perf_control.PerfControl._CPU_ONLINE_FMT % cpu
         self.assertEquals('1',
-                          self._device.old_interface.GetFileContents(path)[0])
+                          self._device.ReadFile(path)[0])
         path = perf_control.PerfControl._SCALING_GOVERNOR_FMT % cpu
         self.assertEquals('performance',
-                          self._device.old_interface.GetFileContents(path)[0])
+                          self._device.ReadFile(path)[0])
     finally:
       perf.SetDefaultPerfMode()
 
diff --git a/android/pylib/perf/thermal_throttle.py b/android/pylib/perf/thermal_throttle.py
index 87ae9665a..a125e72fb 100644
--- a/android/pylib/perf/thermal_throttle.py
+++ b/android/pylib/perf/thermal_throttle.py
@@ -14,8 +14,7 @@ class OmapThrottlingDetector(object):
 
   @staticmethod
   def IsSupported(device):
-    return device.old_interface.FileExistsOnDevice(
-        OmapThrottlingDetector.OMAP_TEMP_FILE)
+    return device.FileExists(OmapThrottlingDetector.OMAP_TEMP_FILE)
 
   def __init__(self, device):
     self._device = device
@@ -34,8 +33,7 @@ class OmapThrottlingDetector(object):
       return float([s for s in log_line.split() if s.isdigit()][0]) / 1000.0
 
   def GetCurrentTemperature(self):
-    tempdata = self._device.old_interface.GetFileContents(
-        OmapThrottlingDetector.OMAP_TEMP_FILE)
+    tempdata = self._device.ReadFile(OmapThrottlingDetector.OMAP_TEMP_FILE)
     return float(tempdata[0]) / 1000.0
 
 
@@ -43,7 +41,7 @@ class ExynosThrottlingDetector(object):
   """Class to detect and track thermal throttling on an Exynos 5."""
   @staticmethod
   def IsSupported(device):
-    return device.old_interface.FileExistsOnDevice('/sys/bus/exynos5-core')
+    return device.FileExists('/sys/bus/exynos5-core')
 
   def __init__(self, device):
     pass
diff --git a/android/pylib/screenshot.py b/android/pylib/screenshot.py
index a09bc3d0a..d2e7c956c 100644
--- a/android/pylib/screenshot.py
+++ b/android/pylib/screenshot.py
@@ -86,7 +86,6 @@ class VideoRecorder(object):
     Returns:
       Output video file name on the host.
     """
-    self._device.old_interface.PullFileFromDevice(
-        self._device_file, self._host_file)
+    self._device.PullFile(self._device_file, self._host_file)
     self._device.RunShellCommand('rm -f "%s"' % self._device_file)
     return self._host_file
diff --git a/android/pylib/uiautomator/test_package.py b/android/pylib/uiautomator/test_package.py
index ecba284aa..d8558c184 100644
--- a/android/pylib/uiautomator/test_package.py
+++ b/android/pylib/uiautomator/test_package.py
@@ -24,5 +24,4 @@ class TestPackage(test_jar.TestJar):
 
   # Override.
   def Install(self, device):
-    device.old_interface.PushIfNeeded(self._jar_path,
-                                      constants.TEST_EXECUTABLE_DIR)
+    device.PushChangedFiles(self._jar_path, constants.TEST_EXECUTABLE_DIR)
diff --git a/android/pylib/utils/reraiser_thread.py b/android/pylib/utils/reraiser_thread.py
index 64196b26e..2964bef1e 100644
--- a/android/pylib/utils/reraiser_thread.py
+++ b/android/pylib/utils/reraiser_thread.py
@@ -74,9 +74,8 @@ class ReraiserThread(threading.Thread):
     """Overrides Thread.run() to add support for reraising exceptions."""
     try:
       self._ret = self._func(*self._args, **self._kwargs)
-    except:
+    except: # pylint: disable=W0702
       self._exc_info = sys.exc_info()
-      raise
 
 
 class ReraiserThreadGroup(object):
diff --git a/android/pylib/valgrind_tools.py b/android/pylib/valgrind_tools.py
index 8f845fbf1..f11ab03c6 100644
--- a/android/pylib/valgrind_tools.py
+++ b/android/pylib/valgrind_tools.py
@@ -39,7 +39,7 @@ def SetChromeTimeoutScale(device, scale):
     # Delete if scale is None/0.0/1.0 since the default timeout scale is 1.0
     device.RunShellCommand('rm %s' % path)
   else:
-    device.old_interface.SetProtectedFileContents(path, '%f' % scale)
+    device.WriteFile(path, '%f' % scale, as_root=True)
 
 
 class BaseTool(object):
@@ -173,7 +173,7 @@ class ValgrindTool(BaseTool):
                                 ValgrindTool.VGLOGS_DIR))
     files = self.GetFilesForTool()
     for f in files:
-      self._device.old_interface.PushIfNeeded(
+      self._device.PushChangedFiles(
           os.path.join(DIR_SOURCE_ROOT, f),
           os.path.join(ValgrindTool.VG_DIR, os.path.basename(f)))
 
diff --git a/android/tombstones.py b/android/tombstones.py
index 1112a97c8..e7549ff73 100755
--- a/android/tombstones.py
+++ b/android/tombstones.py
@@ -62,8 +62,7 @@ def _GetTombstoneData(device, tombstone_file):
   Returns:
     A list of lines
   """
-  return device.old_interface.GetProtectedFileContents(
-      '/data/tombstones/' + tombstone_file)
+  return device.ReadFile('/data/tombstones/' + tombstone_file, as_root=True)
 
 
 def _EraseTombstone(device, tombstone_file):