[Android] Add known devices flag for host_info.

testing/scripts/host_info.py

 #!/usr/bin/env python
 # Copyright 2015 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 json
 import multiprocessing
 import os
 import platform
 import subprocess
@@ skipping 39 matching lines @@
   """Parses the device info for each attached device, and returns a summary
   of the device info and any mismatches.
 
   Returns:
     A dict indicating the result.
   """
   if not is_linux():
     return {}
 
   with common.temporary_file() as tempfile_path:
-    rc = common.run_command([
-        sys.executable,
+    test_cmd = [
+        sys.executeable,

[shatch, 2016/08/04 16:47:02]

Is this right?

[rnephew (Reviews Here), 2016/08/04 16:50:48]

Would you believe me if I said yes?
Fixed.

[shatch, 2016/08/04 16:58:02]

haha

         os.path.join(args.paths['checkout'],
                      'third_party',
                      'catapult',
                      'devil',
                      'devil',
                      'android',
                      'tools',
                      'device_status.py'),
         '--json-output', tempfile_path,
         '--blacklist-file', os.path.join(
-            args.paths['checkout'], 'out', 'bad_devices.json')])
+              args.paths['checkout'], 'out', 'bad_devices.json')
+    ]
+    if args.known_devices_file:
+      test_cmd.extend(['--known-devices-file', args.known_devices_file])
 
+    rc = common.run_command(test_cmd)
     if rc:
       failures.append('device_status')
       return {}
 
     with open(tempfile_path, 'r') as src:
       device_info = json.load(src)
 
   results = {}
   results['devices'] = sorted(v['serial'] for v in device_info)
 
@@ skipping 53 matching lines @@
 def main_compile_targets(args):
   json.dump([], args.output)
 
 
 if __name__ == '__main__':
   funcs = {
     'run': main_run,
     'compile_targets': main_compile_targets,
   }
   sys.exit(common.run_script(sys.argv[1:], funcs))