Move NetworkIconPurger functionality to ActiveNetworkIcon

NetworkIconPurger was added before ActiveNetworkIcon was introduced.
It now makes sense to move the very limited functionality to
ActiveNetworkIcon which already implements the required observer and
interface.

Bug: 862420
Change-Id: I6aa1a28ae18050563786f592beb082f32117ddb2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611873
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661383}
8 files changed