Add ability for NetLogLogger to gather data from more than just NetLog
This includes data from other net-internals tabs and from pending
URLRequests. This also changes the semantices of NetLogLogger so
that it takes the input file in StartObserving and closes it in
StopObserving, to make thread restrictions when using the new
capability a little simpler.
This CL also fixes a number of cases where StopObserving either wasn't
being called, or was being called incorrectly by consumers.
BUG=426918
Review URL: https://codereview.chromium.org/
976483002
Cr-Commit-Position: refs/heads/master@{#320745}