apk_operations: allow downgrade for bundle installs

We allow downgrades by default when installing APKs. We should apply the
same setting for App Bundles. There's no good reason to not allow
downgrades by default for local development, since it's just annoying
when installation fails because a previous install had a higher version.

Note: this does not allow downgrades on user builds, but
"allow_downgrade" is otherwise harmless to pass (the install acts as if
allow_downgrade was not specified).

This is a follow-up to https://crrev.com/c/1383575.

Bug: 915431
Test: manual
Change-Id: I7392d9a4656f702266f5790bee9a7fec395190f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1746642Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686676}

build/android/apk_operations.py

@@ -231,7 +231,7 @@ def _InstallBundle(devices, bundle_apks, package_name, command_line_flags_file,
     # NOTE: For now, installation requires running 'bundletool install-apks'.
     # TODO(digit): Add proper support for bundles to devil instead, then use it.
     install_cmd_args = [
-        'install-apks', '--apks=' + bundle_apks,
+        'install-apks', '--apks=' + bundle_apks, '--allow-downgrade',
         '--adb=' + adb_wrapper.AdbWrapper.GetAdbPath(),
         '--device-id=' + device.serial
     ]