AW: script to remove system image WebView

No change to the product, this only adds a python script for developers.

This adds a script to remove the pre-installed system image WebView
APKs. This is an adaptation of the guide at
https://www.chromium.org/developers/how-tos/build-instructions-android-webview#TOC-Building

R=jbudorick@chromium.org, torne@chromium.org

Test: adb shell ls /system/app/webview /system/app/WebViewGoogle /system/app/WebViewStub
Test: adb shell pm path com.android.webview
Test: adb shell pm path com.google.android.webview
Change-Id: Ib4a9c9706b15aa4c8ec826eb552a4b7552cff129
Reviewed-on: https://chromium-review.googlesource.com/c/1281964
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600876}

android_webview/tools/remove_preinstalled_webview.py

+#!/usr/bin/env python
+#
+# Copyright 2018 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.
+
+"""Removes the preinstalled WebView on a device to avoid signature mismatches.
+
+This should only be used by developers. This script will fail on actual user
+devices (and this configuration is not recommended for user devices).
+
+The recommended development configuration for Googlers is to satisfy all of the
+below:
+  1. The device has a Google-provided image.
+  2. The device does not have an image based on AOSP.
+  3. Set `use_signing_keys = true` in GN args.
+
+If any of the above are not satisfied (or if you're external to Google), you can
+use this script to remove the system-image WebView on your device, which will
+allow you to install a local WebView build without triggering signature
+mismatches (which would otherwise block installing the APK).
+
+After running this script, you should be able to build and install
+system_webview_apk.
+  * If your device does *not* have an AOSP-based image, you will need to set
+    `system_webview_package_name = "com.google.android.webview"` in GN args.
+"""
+
+from __future__ import print_function
+
+import argparse
+import logging
+import os
+import sys
+
+
+sys.path.append(os.path.join(
+    os.path.dirname(__file__), os.pardir, os.pardir, 'build', 'android'))
+import devil_chromium  # pylint: disable=import-error
+from devil.android import device_utils  # pylint: disable=import-error
+from devil.android.sdk import keyevent  # pylint: disable=import-error
+from devil.android.sdk import version_codes  # pylint: disable=import-error
+from devil.android.tools import script_common  # pylint: disable=import-error
+from devil.android.tools import system_app  # pylint: disable=import-error
+
+
+WEBVIEW_SYSTEM_IMAGE_PATHS = ['/system/app/webview',
+                              '/system/app/WebViewGoogle',
+                              '/system/app/WebViewStub']
+WEBVIEW_PACKAGES = ['com.android.webview', 'com.google.android.webview']
+
+
+def _UnlockDevice(device):
+  device.SendKeyEvent(keyevent.KEYCODE_MENU)
+
+
+def UninstallWebViewSystemImages(device):
+  """Uninstalls system images for known WebView packages."""
+  print('Removing system images from %s...' % device.serial)
+  system_app.RemoveSystemApps(device, WEBVIEW_PACKAGES)
+  _UnlockDevice(device)
+
+
+def UninstallWebViewUpdates(device):
+  """Uninstalls updates for WebView packages, if updates exist."""
+  print('Uninstalling updates from %s...' % device.serial)
+  for webview_package in WEBVIEW_PACKAGES:
+    paths = device.GetApplicationPaths(webview_package)
+    if not paths:
+      return  # Package isn't installed, nothing to do
+    if set(paths) <= set(WEBVIEW_SYSTEM_IMAGE_PATHS):
+      # If we only have preinstalled paths, don't try to uninstall updates
+      # (necessary, otherwise we will raise an exception on some devices).
+      return
+    device.Uninstall(webview_package)
+
+
+def AllowStandaloneWebView(device):
+  if device.build_version_sdk < version_codes.NOUGAT:
+    return
+  allow_standalone_webview = ['cmd', 'webviewupdate',
+                              'enable-redundant-packages']
+  device.RunShellCommand(allow_standalone_webview, check_return=True)
+
+
+def RemovePreinstalledWebViews(device):
+  device.EnableRoot()
+  UninstallWebViewUpdates(device)
+  UninstallWebViewSystemImages(device)
+  AllowStandaloneWebView(device)
+
+
+def main():
+  parser = argparse.ArgumentParser(description="""
+Removes the preinstalled WebView APKs to avoid signature mismatches during
+development.
+""")
+
+  parser.add_argument('--verbose', '-v', default=False, action='store_true')
+  parser.add_argument('--quiet', '-q', default=False, action='store_true')
+  script_common.AddEnvironmentArguments(parser)
+  script_common.AddDeviceArguments(parser)
+
+  args = parser.parse_args()
+  if args.verbose:
+    logging.basicConfig(stream=sys.stderr, level=logging.INFO)
+  elif args.quiet:
+    logging.basicConfig(stream=sys.stderr, level=logging.ERROR)
+  else:
+    logging.basicConfig(stream=sys.stderr, level=logging.WARN)
+
+  devil_chromium.Initialize()
+  script_common.InitializeEnvironment(args)
+
+  devices = device_utils.DeviceUtils.HealthyDevices(device_arg=args.devices)
+  device_utils.DeviceUtils.parallel(devices).pMap(RemovePreinstalledWebViews)
+
+
+if __name__ == '__main__':
+  sys.exit(main())