Change VideoRtpReceiver to create remote VideoTrack and VideoTrackSource.

This enabled us to be able to remove VideoTrack::GetSink and RemoteVideoCapturer.

Since video frames from the decoder is delivered on a media engine internal thread, VideoBroadCaster must be made thread safe.

BUG=webrtc:5426
R=deadbeef@webrtc.org, pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1765423005 .

Cr-Commit-Position: refs/heads/master@{#11944}
diff --git a/webrtc/api/api_tests.gyp b/webrtc/api/api_tests.gyp
index 53285f9..bb706dc 100644
--- a/webrtc/api/api_tests.gyp
+++ b/webrtc/api/api_tests.gyp
@@ -37,14 +37,13 @@
         'fakemetricsobserver.h',
         'jsepsessiondescription_unittest.cc',
         'localaudiosource_unittest.cc',
-	'mediaconstraintsinterface_unittest.cc',
+        'mediaconstraintsinterface_unittest.cc',
         'mediastream_unittest.cc',
         'peerconnection_unittest.cc',
         'peerconnectionendtoend_unittest.cc',
         'peerconnectionfactory_unittest.cc',
         'peerconnectioninterface_unittest.cc',
         # 'peerconnectionproxy_unittest.cc',
-        'remotevideocapturer_unittest.cc',
         'rtpsenderreceiver_unittest.cc',
         'statscollector_unittest.cc',
         'test/fakeaudiocapturemodule.cc',