Reland "Rewrite WebRtcSession media tests as PeerConnection tests"

This is a reland of 3df5dcac9b339ba4d3f4969602f094c2c8035b51
Original change's description:
> Rewrite WebRtcSession media tests as PeerConnection tests
> 
> Bug: webrtc:8222
> Change-Id: I782a3227e30de70eb8f6c26a48723cb3510a84ad
> Reviewed-on: https://webrtc-review.googlesource.com/6640
> Commit-Queue: Steve Anton <steveanton@webrtc.org>
> Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20364}

Bug: webrtc:8222
Change-Id: I0a5398170d469eb9223bc781bfb417a85a72a2d2
Reviewed-on: https://webrtc-review.googlesource.com/14380
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20377}
diff --git a/pc/BUILD.gn b/pc/BUILD.gn
index c77a638..02a8e9a 100644
--- a/pc/BUILD.gn
+++ b/pc/BUILD.gn
@@ -394,7 +394,9 @@
       "peerconnection_crypto_unittest.cc",
       "peerconnection_ice_unittest.cc",
       "peerconnection_integrationtest.cc",
+      "peerconnection_media_unittest.cc",
       "peerconnection_rtp_unittest.cc",
+      "peerconnection_signaling_unittest.cc",
       "peerconnectionendtoend_unittest.cc",
       "peerconnectionfactory_unittest.cc",
       "peerconnectioninterface_unittest.cc",
@@ -463,7 +465,9 @@
       "../api/audio_codecs:builtin_audio_encoder_factory",
       "../api/audio_codecs/L16:audio_decoder_L16",
       "../api/audio_codecs/L16:audio_encoder_L16",
+      "../call:call_interfaces",
       "../logging:rtc_event_log_api",
+      "../logging:rtc_event_log_impl",
       "../media:rtc_audio_video",
       "../media:rtc_data",  # TODO(phoglund): AFAIK only used for one sctp constant.
       "../media:rtc_media_base",