[driver] output verbose logging from flutter driver

scripts/slave/recipes/flutter/flutter.py

 # Copyright 2016 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 contextlib
 
 DEPS = [
   'depot_tools/git',
   'file',
   'gsutil',
@@ skipping 43 matching lines @@
   _pub_test('packages/flx')
   _pub_test('packages/newton')
 
   _flutter_test('examples/stocks')
 
 def TestCreateAndLaunch(api):
   with MakeTempDir(api) as temp_dir:
     api.step('test create', ['flutter', 'create', '--with-driver-test',
         'sample_app'], cwd=temp_dir)
     app_path = temp_dir.join('sample_app')
-    api.step('drive sample_app', ['flutter', 'drive'], cwd=app_path)
+    api.step('drive sample_app', ['flutter', 'drive', '--verbose'],
+        cwd=app_path, ok_ret=(0, 1))
 
 # TODO(eseidel): Would be nice to have this on api.path or api.file.
 @contextlib.contextmanager
 def MakeTempDir(api):
   try:
     temp_dir = api.path.mkdtemp('tmp')
     yield temp_dir
   finally:
     api.file.rmtree('temp dir', temp_dir)
 
@@ skipping 158 matching lines @@
     yield test
 
   yield (
     api.test('mac_cannot_find_xcode') +
     api.platform('mac', 64) +
     api.properties(clobber='') +
     api.step_data('enumerate_xcode_installations', api.json.output({
       'installations': {}
     }))
   )