Use network_config.mojo in TrayNetworkStateObserver

This CL also replaces TrayNetworkStateObserver::Delegate with an
Observer so that a single instance can be shared with all system tray
code.

Bug: 862420
Change-Id: I413dc13f2826f9d1ebe116fef1a74624c16b91ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1612361
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661516}
15 files changed