Update from https://crrev.com/306901

build/android/pylib/device/adb_wrapper.py

Index: build/android/pylib/device/adb_wrapper.py
diff --git a/build/android/pylib/device/adb_wrapper.py b/build/android/pylib/device/adb_wrapper.py
index 4981f28df033f82966c76ea6ceb8679bcb05430b..e73d66c9a7c8efe0dbe0c445e7cf61b893ae1591 100644
--- a/build/android/pylib/device/adb_wrapper.py
+++ b/build/android/pylib/device/adb_wrapper.py
@@ -8,6 +8,7 @@ This is a thin wrapper around the adb interface. Any additional complexity
 should be delegated to a higher level (ex. DeviceUtils).
 """
 
+import collections
 import errno
 import logging
 import os
@@ -36,6 +37,10 @@ def _VerifyLocalFileExists(path):
     raise IOError(errno.ENOENT, os.strerror(errno.ENOENT), path)
 
 
+DeviceStat = collections.namedtuple('DeviceStat',
+                                    ['st_mode', 'st_size', 'st_time'])
+
+
 class AdbWrapper(object):
   """A wrapper around a local Android Debug Bridge executable."""
 
@@ -200,6 +205,38 @@ class AdbWrapper(object):
             args, output, status, self._device_serial)
     return output
 
+  def Ls(self, path, timeout=_DEFAULT_TIMEOUT, retries=_DEFAULT_RETRIES):
+    """List the contents of a directory on the device.
+
+    Args:
+      path: Path on the device filesystem.
+      timeout: (optional) Timeout per try in seconds.
+      retries: (optional) Number of retries to attempt.
+
+    Returns:
+      A list of pairs (filename, stat) for each file found in the directory,
+      where the stat object has the properties: st_mode, st_size, and st_time.
+
+    Raises:
+      AdbCommandFailedError if |path| does not specify a valid and accessible
+          directory in the device.
+    """
+    def ParseLine(line):
+      cols = line.split(None, 3)
+      filename = cols.pop()
+      stat = DeviceStat(*[int(num, base=16) for num in cols])
+      return (filename, stat)
+
+    cmd = ['ls', path]
+    lines = self._RunDeviceAdbCmd(
+        cmd, timeout=timeout, retries=retries).splitlines()
+    if lines:
+      return [ParseLine(line) for line in lines]
+    else:
+      raise device_errors.AdbCommandFailedError(
+          cmd, 'path does not specify an accessible directory in the device',
+          device_serial=self._device_serial)
+
   def Logcat(self, filter_spec=None, timeout=_DEFAULT_TIMEOUT,
              retries=_DEFAULT_RETRIES):
     """Get the logcat output.