RTC[In/Out]boundRTPStreamStats: qpSum,framesDecoded,framesEncoded added.

Recently added to the spec:
RTCRTPStreamStats.qpSum - https://w3c.github.io/webrtc-stats/#dom-rtcrtpstreamstats-qpsum
RTCInboundRTPStreamStats.framesDecoded - https://w3c.github.io/webrtc-stats/#dom-rtcinboundrtpstreamstats-framesdecoded
RTCOutboundRTPStreamStats.framesEncoded - https://w3c.github.io/webrtc-stats/#dom-rtcoutboundrtpstreamstats-framesencoded

These are added and collected. However, the qpSum is only collected in
the outbound case. It should be collected in the inbound case before
closing crbug.com/657855

BUG=chromium:657854, chromium:657855, chromium:657856

Review-Url: https://codereview.webrtc.org/2588373005
Cr-Original-Commit-Position: refs/heads/master@{#15872}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 6769c4941817ac3d5b967d0aafa1304c06d0672e
5 files changed