(Reland) Use logdog butler subcommand to run tests.

build/android/pylib/android/logdog_logcat_monitor.py

 # Copyright 2016 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
 
 from devil.android import logcat_monitor
 from devil.utils import reraiser_thread
 from pylib.utils import logdog_helper
 
@@ skipping 41 matching lines @@
     self._StartRecording()
 
   def _StartRecording(self):
     """Starts recording logcat to file.
 
     Write logcat to stream at the same time.
     """
     def record_to_stream():
       if self._logdog_stream:
         for data in self._adb.Logcat(filter_specs=self._filter_specs,
-                                     logcat_format='threadtime'):
+                                     logcat_format='threadtime',
+                                     iter_timeout=0.05):

[jbudorick, 2017/03/17 19:20:21]

This *might* be spinning too much. How's the performance with a slightly higher
timeout value?

[BigBossZhiling, 2017/03/20 22:09:50]

Acknowledged.

           if self._stop_recording_event.isSet():
             return
-          self._logdog_stream.write(data + '\n')
+          if data:
+            self._logdog_stream.write(data + '\n')
 
     self._stop_recording_event.clear()
     if not self._record_thread:
       self._record_thread = reraiser_thread.ReraiserThread(record_to_stream)
       self._record_thread.start()
 
   def Close(self):
     """Override parent's close method."""
     pass
 
   def __del__(self):
     """Override parent's delete method."""
     pass