Propagate SDP negotiation of extmap-allow-mixed to RtpHeaderExtensionMap

Bug: webrtc:7990
Change-Id: I662595f90b9d0be39f7e14752e13b2bb7a1746ee
Reviewed-on: https://webrtc-review.googlesource.com/c/106020
Reviewed-by: Seth Hampson <shampson@webrtc.org>
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Johannes Kron <kron@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25421}
diff --git a/audio/audio_send_stream_unittest.cc b/audio/audio_send_stream_unittest.cc
index e17030f..6a92329 100644
--- a/audio/audio_send_stream_unittest.cc
+++ b/audio/audio_send_stream_unittest.cc
@@ -198,6 +198,7 @@
     EXPECT_CALL(*channel_proxy_, SetRTCP_CNAME(StrEq(kCName))).Times(1);
     EXPECT_CALL(*channel_proxy_, SetNACKStatus(true, 10)).Times(1);
     EXPECT_CALL(*channel_proxy_, SetFrameEncryptor(_)).Times(1);
+    EXPECT_CALL(*channel_proxy_, SetExtmapAllowMixed(false)).Times(1);
     EXPECT_CALL(*channel_proxy_,
                 SetSendAudioLevelIndicationStatus(true, kAudioLevelId))
         .Times(1);
@@ -330,10 +331,11 @@
   config.send_codec_spec->transport_cc_enabled = false;
   config.send_codec_spec->cng_payload_type = 42;
   config.encoder_factory = MockAudioEncoderFactory::CreateUnusedFactory();
+  config.rtp.extmap_allow_mixed = true;
   config.rtp.extensions.push_back(
       RtpExtension(RtpExtension::kAudioLevelUri, kAudioLevelId));
   EXPECT_EQ(
-      "{rtp: {ssrc: 1234, extensions: [{uri: "
+      "{rtp: {ssrc: 1234, extmap-allow-mixed: true, extensions: [{uri: "
       "urn:ietf:params:rtp-hdrext:ssrc-audio-level, id: 2}], nack: "
       "{rtp_history_ms: 0}, c_name: foo_name}, send_transport: null, "
       "media_transport: null, "