[Android] Thread names reflect the device serial number they are associated with.

build/android/pylib/utils/run_tests_helper.py

Index: build/android/pylib/utils/run_tests_helper.py
diff --git a/build/android/pylib/utils/run_tests_helper.py b/build/android/pylib/utils/run_tests_helper.py
index b5730b6893aa544b2096772fc95180fd992b3d7a..32275970d90fac2a3e723f6cbe6753fe4ecd9524 100644
--- a/build/android/pylib/utils/run_tests_helper.py
+++ b/build/android/pylib/utils/run_tests_helper.py
@@ -13,7 +13,7 @@ class CustomFormatter(logging.Formatter):
   """Custom log formatter."""
 
   #override
-  def __init__(self, fmt=''):
+  def __init__(self, fmt='%(threadName)-4s  %(message)s'):
     # Can't use super() because in older Python versions logging.Formatter does
     # not inherit from object.
     logging.Formatter.__init__(self, fmt=fmt)
@@ -24,8 +24,10 @@ class CustomFormatter(logging.Formatter):
     # Can't use super() because in older Python versions logging.Formatter does
     # not inherit from object.
     msg = logging.Formatter.format(self, record)
+    if 'MainThread' in msg[:19]:
+      msg = msg.replace('MainThread', 'Main', 1)
     timediff = str(int(time.time() - self._creation_time))
-    return '%s %ss  %s' % (record.levelname[0], timediff.rjust(4), msg)
+    return '%s %ss %s' % (record.levelname[0], timediff.rjust(4), msg)
 
 
 def GetExpectations(file_name):