Added dependencies used by MockRtpTransportControllerSend to its header file. The mocked interface can't be used properly without those. This prepares for later CLs utilizing the mock. Bug: None Change-Id: I5f8ca04032ad09810240f7c034cc628d700dbedb Reviewed-on: https://webrtc-review.googlesource.com/56181 Reviewed-by: Niels Moller <nisse@webrtc.org> Commit-Queue: Sebastian Jansson <srte@webrtc.org> Cr-Commit-Position: refs/heads/master@{#22154}