AW: improve command_line tool

This improves the adb_command_line tool as follows:

 * For WebView, throw an exception if someone tries to use this on a
   user device (WebView won't respect the flags anyway)
 * For Chrome, log a warning on user devices (Chrome is slightly more
   relaxed, but usually won't respect flags)
 * Minor refactoring to use already-existing helper methods to add some
   flags (no significant change to behavior here though).

R=agrieve@chromium.org

Bug: 918727
Test: Manual (try to write flags on user and userdebug emulators)
Change-Id: I78dc223bd882fc41d47d19bac6b2b2a26a6a53ac
Reviewed-on: https://chromium-review.googlesource.com/c/1458369
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630131}

build/android/adb_command_line.py

@@ -6,14 +6,17 @@
 """Utility for reading / writing command-line flag files on device(s)."""
 
 import argparse
-import os
+import logging
 import sys
 
-import devil_chromium
+import devil_chromium  # pylint: disable=import-error, unused-import
 
+from devil.android import device_errors
 from devil.android import device_utils
 from devil.android import flag_changer
+from devil.android.tools import script_common
 from devil.utils import cmd_helper
+from devil.utils import logging_common
 
 
 def main():
@@ -25,17 +28,17 @@ Empty string: Deletes command-line file.
 Otherwise: Writes command-line file.
 
 '''
-  parser.add_argument('-d', '--device', dest='devices', action='append',
-                      default=[], help='Target device serial (repeatable).')
   parser.add_argument('--name', required=True,
                       help='Name of file where to store flags on the device.')
   parser.add_argument('-e', '--executable', dest='executable', default='chrome',
                       help='(deprecated) No longer used.')
-  parser.add_argument('--adb-path', type=os.path.abspath,
-                      help='Path to the adb binary.')
-  args, remote_args = parser.parse_known_args()
+  script_common.AddEnvironmentArguments(parser)
+  script_common.AddDeviceArguments(parser)
+  logging_common.AddLoggingArguments(parser)
 
-  devil_chromium.Initialize(adb_path=args.adb_path)
+  args, remote_args = parser.parse_known_args()
+  script_common.InitializeEnvironment(args)
+  logging_common.InitializeLogging(args)
 
   devices = device_utils.DeviceUtils.HealthyDevices(device_arg=args.devices,
                                                     default_retries=0)
@@ -52,7 +55,19 @@ Otherwise: Writes command-line file.
   else:
     action = 'Wrote command line file. '
 
+  is_webview = args.name == 'webview-command-line'
+
   def update_flags(device):
+    if device.IsUserBuild() and is_webview:
+      raise device_errors.CommandFailedError(
+          'WebView only respects flags on a userdebug or eng device, yours '
+          'is a user build.', device)
+    elif device.IsUserBuild():
+      logging.warning(
+          'Your device (%s) is a user build; Chrome may or may not pick up '
+          'your commandline flags. Check your '
+          '"command_line_on_non_rooted_enabled" preference, or switch '
+          'devices.', device)
     changer = flag_changer.FlagChanger(device, args.name)
     if remote_args is not None:
       flags = changer.ReplaceFlags(remote_args)