[App Management] Implement App Service updates for installation/uninstallation of extensions.

This CL implements the OnExtensionInstalled and OnExtensionUninstalled
methods of the ExtensionApps App Service publisher, so that updates are
sent to the App Service subscribers. This allows live updates to be
observed when apps are installed or uninstalled in the UI.

Bug: 906508
Change-Id: Ic14b7f1b49ccfd77e9f90fe2956dfa4c09af069b
Reviewed-on: https://chromium-review.googlesource.com/c/1404547
Reviewed-by: Nigel Tao <nigeltao@chromium.org>
Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: Reka Norman <rekanorman@google.com>
Cr-Commit-Position: refs/heads/master@{#622361}
2 files changed