Plumbing in preparation for standardized getStats() in webrtc-internals.

This CL implements the calling chain from webrtc_internals.js all the
way to getStats() and back, including process hops and layering.
- This adds the calling chain for standard getStats() API. The original
calling chain for legacy getStats() remains intact, but is renamed. implements invoking the standard API and
formats the result in the way that webrtc_internals.js expects stats to
be formatted.

These are roughly the layers:
- webrtc_internals.js "get[Legacy/Standard]Stats"
- WebRTCInternalsMessageHandler::OnGet[Legacy/Standard]Stats
- PeerConnectionTracker::OnGet[Legacy/Standard]Stats
- webrtc::PeerConnectionInterface::GetStats
- Internal[Legacy/Standard]StatsObserver::[OnComplete/OnStatsDelivered]
- PeerConnectionTrackerHost::OnAdd[Legacy/Standard]Stats
- WebRTCInternals::OnAdd[Legacy/Standard]Stats
- WebRTCInternalsMessageHandler::OnUpdate
- webrtc_internals.js "add[Legacy/Standard]Stats"

This CL is split up from
to ease reviewing. The new calling chain is NOT exercised in this CL,
this will be handled in a follow-up CL.

Bug: 803014
Change-Id: Ied4b0b8f136f92aaad4633edb38ccb288e41ef3f
Reviewed-by: Guido Urdaneta <>
Reviewed-by: Kinuko Yasuda <>
Auto-Submit: Henrik Boström <>
Commit-Queue: Henrik Boström <>
Cr-Commit-Position: refs/heads/master@{#653118}
14 files changed