DevX: use devil_chromium.Initialize in CLI script

This swaps script_common.InitializeEnvironment() for
devil_chromium.Initialize(). These two methods are mutually exclusive
(calling both turns the latter into a NOOP, as
devil_env.config.Initialize() only has an effect the first time it's
called).

This changes the default 'adb' to be the one in chromium's Android SDK
(v40) rather than devil's default (v32). This continues to support the
'--adb-path' switch.

Bug: 978697
Test: build/android/adb_system_webview_command_line -vv (uses //third_party/android_sdk/public/platform-tools/adb)
Test: build/android/adb_system_webview_command_line -vv --adb-path=`which adb` (uses specified adb)
Change-Id: I8ba4eb683f47eeed758a935455a39b9dcef113f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1692201
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675821}

build/android/adb_command_line.py

@@ -11,7 +11,7 @@ import argparse
 import logging
 import sys
 
-import devil_chromium  # pylint: disable=import-error, unused-import
+import devil_chromium
 
 from devil.android import device_errors
 from devil.android import device_utils
@@ -53,7 +53,7 @@ Otherwise: Writes command-line file.
   logging_common.AddLoggingArguments(parser)
 
   args, remote_args = parser.parse_known_args()
-  script_common.InitializeEnvironment(args)
+  devil_chromium.Initialize(adb_path=args.adb_path)
   logging_common.InitializeLogging(args)
 
   devices = device_utils.DeviceUtils.HealthyDevices(device_arg=args.devices,