[test_runner] support relative paths on argument --shared-prefs-file

build/android/test_runner.py

Index: build/android/test_runner.py
diff --git a/build/android/test_runner.py b/build/android/test_runner.py
index b22607fa4c1b34fc3e94f4bf6fd5755ea12baac1..c02c4466da1f72df8ab35eca5963799f201930ec 100755
--- a/build/android/test_runner.py
+++ b/build/android/test_runner.py
@@ -420,7 +420,7 @@ def AddInstrumentationTestOptions(parser):
       help='Capture screenshots of test failures')
   parser.add_argument(
       '--shared-prefs-file',
-      dest='shared_prefs_file', type=os.path.realpath,
+      dest='shared_prefs_file', type=os.path.abspath,

[shenghuazhang, 2017/07/25 20:44:45]

Type realpath changes value "//home/..." to "/home/...", so set it to abspath
here, and handle the realpath below.

[jbudorick, 2017/07/25 21:07:46]

I think you're on the right track here, but you can do this more concisely by
taking advantage of the fact that what we pass to type doesn't have to be an
actual type -- it can be a function (as abspath and realpath are). If you write
a function that takes a string, does the same manipulation you've got in the if
block below, and then returns the result, you should be able to use that here
and reuse it later for other path arguments.

[shenghuazhang, 2017/07/25 21:28:10]

Thanks for this suggestion! This should be much more clean and reusable.

       help='The relative path to a file containing JSON list of shared '
            'preference files to edit and how to do so. Example list: '
            '[{'
@@ -967,6 +967,13 @@ def main():
     parser.error('--replace-system-package and --enable-concurrent-adb cannot '
                  'be used together')
 
+  if hasattr(args, 'shared_prefs_file') and args.shared_prefs_file:
+    if args.shared_prefs_file.startswith('//'):
+      args.shared_prefs_file = os.path.abspath(
+          os.path.join(host_paths.DIR_SOURCE_ROOT,
+                       args.shared_prefs_file[2:].replace('/', os.sep)))
+    args.shared_prefs_file = os.path.realpath(args.shared_prefs_file)
+
   try:
     return RunTestsCommand(args)
   except base_error.BaseError as e: