This CL fixes the problem of misfired negotiationneeded notifications due to the lack of a NegotiationNeeded slot and the proper procedure to update it. Change-Id: Ie273c691f11316c9846606446f6cf838226b5d5c Bug: chromium:740501 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131283 Commit-Queue: Guido Urdaneta <guidou@webrtc.org> Reviewed-by: Steve Anton <steveanton@webrtc.org> Reviewed-by: Henrik Boström <hbos@webrtc.org> Reviewed-by: Magnus Jedvert <magjed@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27594}