Put screenshot.py back to work

build/android/screenshot.py

Index: build/android/screenshot.py
diff --git a/build/android/screenshot.py b/build/android/screenshot.py
index fb1aee1d985aaedef0c47c22605328ff4ca969bd..e3a2609f31764e2354dbd8c2c435da878ca1f62b 100755
--- a/build/android/screenshot.py
+++ b/build/android/screenshot.py
@@ -72,6 +72,8 @@ def main():
   if not options.device and len(android_commands.GetAttachedDevices()) > 1:
     parser.error('Multiple devices are attached. '
                  'Please specify device serial number with --device.')
+  elif not options.device and len(android_commands.GetAttachedDevices()) == 1:

[jbudorick, 2014/12/16 02:18:51]

Couple of problems in here:
 - We're no longer using android_commands in new code. adb_wrapper.GetDevices()
from b/a/pylib/device/adb_wrapper.py is what you're looking for.
 - No need to call that 3 times -- just call it once and store the result.

[Ian Wen, 2014/12/16 18:11:52]

Did a small improvement by storing it locally. However it seems
adb_wrapper.GetDevices() is not a static method; it needs to initialize
AdbWrapper instance, which takes device number as arguments.

+    options.device = android_commands.GetAttachedDevices()[0]
 
   if len(args) > 1:
     parser.error('Too many positional arguments.')