Delete class WebrtcDummyVideoCapturer

Replaced with a DummyVideoTrackSource.

Bug: webrtc:6353
Change-Id: I6da52f7f9ed0611862bcd631d52dadee11bbf014
Reviewed-on: https://chromium-review.googlesource.com/c/1373837
Reviewed-by: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Niels Möller <nisse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616239}
4 files changed