Move active network state tracking to ash::TrayNetworkStateObserver

This CL moves active network state tracking from ActiveNetworkIcon to
TrayNetworkStateObserver in preparation for other Ash UI (e.g. the
network feature pods) to uses the same cached states.

Bug: 862420
Change-Id: I742bb56bfcd54df196f5e4078b85f09c51a809cb
Reviewed-by: Kyle Horimoto <>
Commit-Queue: Steven Bennetts <>
Cr-Commit-Position: refs/heads/master@{#661842}
8 files changed