Reland "Distinguish between send and receive codecs"

This reverts commit 8e8b36a94a7a7a1fd0f8093979a406afa56e18c1.

Reason for revert: The CL has been improved with the following changes,
  - Fixed negotiation of send/receive only clients.
  - Handles the implicit assumption that any H264 decoder also can
    decode H264 constraint baseline.

Original change's description:
> Distinguish between send and receive codecs
>
> Even though send and receive codecs may be the same, they might have
> different support in HW. Distinguish between send and receive codecs
> to be able to keep track of which codecs have HW support.
>
> Bug: chromium:1029737
> Change-Id: Id119560becadfe0aaf861c892a6485f1c2eb378d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/165763
> Commit-Queue: Johannes Kron <kron@webrtc.org>
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#30284}

Change-Id: I834ed48ee78d04922c73e2836165e476925e1cc5
Bug: chromium:1029737
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168605
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Johannes Kron <kron@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30932}
diff --git a/media/base/media_channel.h b/media/base/media_channel.h
index 7ca6002..c2c1b56 100644
--- a/media/base/media_channel.h
+++ b/media/base/media_channel.h
@@ -749,6 +749,10 @@
 
   std::vector<Codec> codecs;
   std::vector<webrtc::RtpExtension> extensions;
+  // For a send stream this is true if we've neogtiated a send direction,
+  // for a receive stream this is true if we've negotiated a receive direction.
+  bool is_stream_active = true;
+
   // TODO(pthatcher): Add streams.
   RtcpParameters rtcp;