[Android] Add record functionality to logcat monitor.

build/android/devil/android/sdk/adb_wrapper.py

Index: build/android/devil/android/sdk/adb_wrapper.py
diff --git a/build/android/devil/android/sdk/adb_wrapper.py b/build/android/devil/android/sdk/adb_wrapper.py
index 38db0e1fc1f1429f73d108663791ac7277aa1f3a..0448238eefcce885438bbcd0b3037ce9ad26e5c9 100644
--- a/build/android/devil/android/sdk/adb_wrapper.py
+++ b/build/android/devil/android/sdk/adb_wrapper.py
@@ -147,7 +147,7 @@ class AdbWrapper(object):
                            device_serial=self._device_serial,
                            check_error=check_error)
 
-  def _IterRunDeviceAdbCmd(self, args, timeout):
+  def _IterRunDeviceAdbCmdLines(self, args, timeout):
     """Runs an adb command and returns an iterator over its output lines.
 
     Args:
@@ -160,6 +160,19 @@ class AdbWrapper(object):
     return cmd_helper.IterCmdOutputLines(
       self._BuildAdbCmd(args, self._device_serial), timeout=timeout)
 
+  def _IterRunDeviceAdbCmd(self, args, timeout):
+    """Runs an adb command and returns an iterator over its output.
+
+    Args:
+      args: A list of arguments to adb.
+      timeout: Timeout in seconds.
+
+    Yields:
+      The current output of the command.
+    """
+    return cmd_helper.IterCmdOutput(
+      self._BuildAdbCmd(args, self._device_serial), timeout=timeout)
+
   def __eq__(self, other):
     """Consider instances equal if they refer to the same device.
 
@@ -375,7 +388,7 @@ class AdbWrapper(object):
           cmd, 'path does not specify an accessible directory in the device',
           device_serial=self._device_serial)
 
-  def Logcat(self, clear=False, dump=False, filter_specs=None,
+  def Logcat(self, clear=False, dump=False, output_file=None, filter_specs=None,
              logcat_format=None, ring_buffer=None, timeout=None,
              retries=_DEFAULT_RETRIES):
     """Get an iterable over the logcat output.
@@ -411,6 +424,8 @@ class AdbWrapper(object):
     if ring_buffer:
       for buffer_name in ring_buffer:
         cmd.extend(['-b', buffer_name])
+    if output_file:
+      cmd.extend(['-f', output_file])
     if filter_specs:
       cmd.extend(filter_specs)