[App Management] Create ExtensionApps instance to publish web apps.

This CL creates a second ExtensionApps instance to act as an App Service
publisher for apps of type AppType.kWeb. This is necessary to allow the
UI to distinguish web apps from other extensions, all of which are
currently published with type AppType.kExtension.

Bug: 906508
Change-Id: Ide6911387ee1aa0c6455d68c11fe46675c4ff4e8
Reviewed-on: https://chromium-review.googlesource.com/c/1427999
Commit-Queue: Reka Norman <rekanorman@google.com>
Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Nigel Tao <nigeltao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626003}
5 files changed