Generalize the reload PLMO to support other transition types.
This change moves tracking of reloads, forward/back navigations
and new navigations into the core PLMO.
It's not unlikely that other observers may want to track load
metrics broken down by load types, so we annotate load types using
suffixes, rather than PageLoad.Clients.LoadType-style naming, which
would not generalize to other observers.
BUG=607063
Review-Url: https://codereview.chromium.org/2091353002
Cr-Commit-Position: refs/heads/master@{#402579}
11 files changed
