[Android] Fix DeviceUtils.__str__ when no serial is provided.

tools/android/mempressure.py

Index: tools/android/mempressure.py
diff --git a/tools/android/mempressure.py b/tools/android/mempressure.py
index bd606f132235f70f1c4c762dff7d1e4f6a117e75..6c6f2717c7a33abfee7ac0ae226e6bdebb7ff6cf 100755
--- a/tools/android/mempressure.py
+++ b/tools/android/mempressure.py
@@ -15,6 +15,7 @@ BUILD_ANDROID_DIR = os.path.join(os.path.dirname(__file__),
                                  'build',
                                  'android')
 sys.path.append(BUILD_ANDROID_DIR)
+from pylib import android_commands
 from pylib import constants
 from pylib import flag_changer
 from pylib.device import device_utils
@@ -85,7 +86,13 @@ def main(argv):
   package = package_info.package
   activity = package_info.activity
 
-  device = device_utils.DeviceUtils(None)
+  devices = android_commands.GetAttachedDevices()
+  if not len(devices):

[frankf, 2014/07/28 22:52:31]

if not devices:

[jbudorick, 2014/07/28 23:05:40]

Done.

+    logging.error('No devices attached.')
+    sys.exit(1)
+  elif len(devices) > 1:
+    logging.warning('Multiple devices attached. Using %s.' % devices[0])
+  device = device_utils.DeviceUtils(devices[0])
 
   try:
     device.EnableRoot()