Changes synchronization offset perfomance tracking to be logged after converge only.
Changes synchronization offset perfomance tracking
to be logged after converge only.

BUG=webrtc:5032, chromium:618226
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/2046943004 .

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#13160}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 371b43b86a6a1bf0fb8a9059309a67a6e16a9542

Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc