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

build/android/pylib/screenshot.py

Index: build/android/pylib/screenshot.py
diff --git a/build/android/pylib/screenshot.py b/build/android/pylib/screenshot.py
index ea939b704ce6fd51fc0f70aac82a86af46cb66f2..b5f2c65acb8578b9535440595227268b5067e945 100644
--- a/build/android/pylib/screenshot.py
+++ b/build/android/pylib/screenshot.py
@@ -73,9 +73,8 @@ class VideoRecorder(object):
     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=signal.SIGINT,
+                                quiet=True):
       logging.warning('Nothing to kill: screenrecord was not running')
     self._recorder.wait()