This removes use of the MockPeerConnection and replaces it with the FakePeerConnectionForStats testing class. Bug: webrtc:8764 Change-Id: I78553c5a4e4d68cb6666a83f443f72f7c25488dc Reviewed-on: https://webrtc-review.googlesource.com/46940 Commit-Queue: Steve Anton <steveanton@webrtc.org> Reviewed-by: Henrik Boström <hbos@webrtc.org> Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org> Cr-Commit-Position: refs/heads/master@{#21882}