(Reland) Use logdog butler subcommand to run tests.

build/android/pylib/android/logdog_logcat_monitor.py

Index: build/android/pylib/android/logdog_logcat_monitor.py
diff --git a/build/android/pylib/android/logdog_logcat_monitor.py b/build/android/pylib/android/logdog_logcat_monitor.py
index a89b9f4ea5369218ce9fb38221012b671e6de710..e966052568ec7a3b865a0632cf0c3d82ad8afb86 100644
--- a/build/android/pylib/android/logdog_logcat_monitor.py
+++ b/build/android/pylib/android/logdog_logcat_monitor.py
@@ -59,10 +59,12 @@ class LogdogLogcatMonitor(logcat_monitor.LogcatMonitor):
     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: