[Android] Add LogcatMonitor.

build/android/pylib/device/adb_wrapper.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.
 
 """This module wraps Android's adb tool.
 
 This is a thin wrapper around the adb interface. Any additional complexity
 should be delegated to a higher level (ex. DeviceUtils).
 """
 
@@ skipping 267 matching lines @@
     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=None):
+  def Logcat(self, clear=False, dump=False, filter_spec=None,
+             logcat_format=None, timeout=None):
     """Get an iterator over the logcat output.
 
     Args:
       filter_spec: (optional) Spec to filter the logcat.
       timeout: (optional) Timeout per try in seconds.
 
     Yields:
       logcat output line by line.
     """
     cmd = ['logcat']
+    if clear:
+      cmd.append('-c')
+    if dump:
+      cmd.append('-d')
+    if logcat_format:
+      cmd.extend(['-v', logcat_format])
     if filter_spec is not None:
       cmd.append(filter_spec)
     return self._IterRunDeviceAdbCmd(cmd, timeout)
 
   def Forward(self, local, remote, timeout=_DEFAULT_TIMEOUT,
               retries=_DEFAULT_RETRIES):
     """Forward socket connections from the local socket to the remote socket.
 
     Sockets are specified by one of:
       tcp:<port>
@@ skipping 170 matching lines @@
     """Restarts the adbd daemon with root permissions, if possible.
 
     Args:
       timeout: (optional) Timeout per try in seconds.
       retries: (optional) Number of retries to attempt.
     """
     output = self._RunDeviceAdbCmd(['root'], timeout, retries)
     if 'cannot' in output:
       raise device_errors.AdbCommandFailedError(
           ['root'], output, device_serial=self._device_serial)