[Android] Add a "quiet" flag so KillAll doesn't complain if no processes killed

build/android/pylib/screenshot.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.
 
 import logging
 import os
-import signal
 import tempfile
 
 from pylib import cmd_helper
+from pylib import device_signal
 from pylib.device import device_errors
 
 # TODO(jbudorick) Remove once telemetry gets switched over.
 import pylib.android_commands
 import pylib.device.device_utils
 
 
 class VideoRecorder(object):
   """Records a screen capture video from an Android Device (KitKat or newer).
 
@@ skipping 45 matching lines @@
         if self._is_started:
           break
     return self._is_started
 
   def Stop(self):
     """Stop recording video."""
     os.remove(self._recorder_stdout)
     self._is_started = False
     if not self._recorder:
       return
-    try:
-      self._device.KillAll('screenrecord', signum=signal.SIGINT)
-    except device_errors.CommandFailedError:
+    if not self._device.KillAll('screenrecord', signum=device_signal.SIGINT,
+                                quiet=True):
       logging.warning('Nothing to kill: screenrecord was not running')
     self._recorder.wait()
 
   def Pull(self, host_file=None):
     """Pull resulting video file from the device.
 
     Args:
       host_file: Path to the video file to store on the host.
     Returns:
       Output video file name on the host.
     """
     host_file_name = host_file or ('screen-recording-%s.mp4' %
                                    self._device.old_interface.GetTimestamp())
     host_file_name = os.path.abspath(host_file_name)
     self._device.old_interface.EnsureHostDirectory(host_file_name)
     self._device.PullFile(self._device_file, host_file_name)
     self._device.RunShellCommand('rm -f "%s"' % self._device_file)
     return host_file_name