VideoAdapterTest: Replace FileVideoCapturer with FakeVideoCapturer
VideoAdapterTest: Replace FileVideoCapturer with FakeVideoCapturer

The unittests are currently flaky due to the use of FileVideoCapturer.

BUG=4317
R=pbos@webrtc.org, pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/49649004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8969}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0184057d540b20009aabf4a0a70386ac4b426c47

dcpang/fatline-libjingle,dcpang/fatline-libjingle,sippet/talk,sippet/talk,sippet/talk,dcpang/fatline-libjingle,dcpang/fatline-libjingle,sippet/talk,sippet/talk,dcpang/fatline-libjingle