Revert "Enable FlexFEC as a receiver video codec by default"

This reverts commit f08db1be94e760c201acdc3a121e67453960c970.

Reason for revert: It looks like this breaks Chromium FYI Windows bots.

See https://ci.chromium.org/p/chromium/builders/webrtc.fyi/WebRTC%20Chromium%20FYI%20Win10%20Tester/6988.

If this is not the culprit I will reland.

Original change's description:
> Enable FlexFEC as a receiver video codec by default
>
> - Add Flex FEC format as default supported receive codec
> - Disallow advertising FlexFEC as video sender codec by default until implementation is complete
> - Toggle field trial "WebRTC-FlexFEC-03-Advertised"s behavior for receiver to use as kill-switch to prevent codec advertising
>
> Bug: webrtc:8151
> Change-Id: Iff367119263496fb335500e96641669654b45834
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/191947
> Commit-Queue: Christoffer Rodbro <crodbro@webrtc.org>
> Reviewed-by: Ying Wang <yinwa@webrtc.org>
> Reviewed-by: Christoffer Rodbro <crodbro@webrtc.org>
> Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#32639}

TBR=brandtr@webrtc.org,tommi@webrtc.org,stefan@webrtc.org,crodbro@webrtc.org,crodbro@google.com,yinwa@webrtc.org,philipp.hancke@googlemail.com,hmaniar@nvidia.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: webrtc:8151
Change-Id: Ia1788a1cf34e0fc9500a081552f6ed03d0995d5b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/194334
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32657}

media/engine/webrtc_video_engine.cc

@@ -67,11 +67,6 @@ bool IsEnabled(const webrtc::WebRtcKeyValueConfig& trials,
   return absl::StartsWith(trials.Lookup(name), "Enabled");
 }
 
-bool IsDisabled(const webrtc::WebRtcKeyValueConfig& trials,
-                absl::string_view name) {
-  return absl::StartsWith(trials.Lookup(name), "Disabled");
-}
-
 bool PowerOfTwo(int value) {
   return (value > 0) && ((value & (value - 1)) == 0);
 }
@@ -112,8 +107,7 @@ void AddDefaultFeedbackParams(VideoCodec* codec,
 // default feedback params to the codecs.
 std::vector<VideoCodec> AssignPayloadTypesAndDefaultCodecs(
     std::vector<webrtc::SdpVideoFormat> input_formats,
-    const webrtc::WebRtcKeyValueConfig& trials,
+    const webrtc::WebRtcKeyValueConfig& trials) {
-    bool is_decoder_factory) {
   if (input_formats.empty())
     return std::vector<VideoCodec>();
   static const int kFirstDynamicPayloadType = 96;
@@ -123,13 +117,7 @@ std::vector<VideoCodec> AssignPayloadTypesAndDefaultCodecs(
   input_formats.push_back(webrtc::SdpVideoFormat(kRedCodecName));
   input_formats.push_back(webrtc::SdpVideoFormat(kUlpfecCodecName));
 
-  // flexfec-03 is supported as
+  if (IsEnabled(trials, "WebRTC-FlexFEC-03-Advertised")) {
-  // - receive codec unless WebRTC-FlexFEC-03-Advertised is disabled
-  // - send codec if WebRTC-FlexFEC-03-Advertised is enabled
-  if ((is_decoder_factory &&
-       !IsDisabled(trials, "WebRTC-FlexFEC-03-Advertised")) ||
-      (!is_decoder_factory &&
-       IsEnabled(trials, "WebRTC-FlexFEC-03-Advertised"))) {
     webrtc::SdpVideoFormat flexfec_format(kFlexfecCodecName);
     // This value is currently arbitrarily set to 10 seconds. (The unit
     // is microseconds.) This parameter MUST be present in the SDP, but
@@ -172,9 +160,7 @@ std::vector<VideoCodec> AssignPayloadTypesAndDefaultCodecs(
 
 // is_decoder_factory is needed to keep track of the implict assumption that any
 // H264 decoder also supports constrained base line profile.
-// Also, is_decoder_factory is used to decide whether FlexFEC video format
+// TODO(kron): Perhaps it better to move the implcit knowledge to the place
-// should be advertised as supported.
-// TODO(kron): Perhaps it is better to move the implicit knowledge to the place
 // where codecs are negotiated.
 template <class T>
 std::vector<VideoCodec> GetPayloadTypesAndDefaultCodecs(
@@ -192,7 +178,7 @@ std::vector<VideoCodec> GetPayloadTypesAndDefaultCodecs(
   }
 
   return AssignPayloadTypesAndDefaultCodecs(std::move(supported_formats),
-                                            trials, is_decoder_factory);
+                                            trials);
 }
 
 bool IsTemporalLayersSupported(const std::string& codec_name) {
@@ -1513,7 +1499,7 @@ void WebRtcVideoChannel::ConfigureReceiverRtp(
 
   // TODO(brandtr): Generalize when we add support for multistream protection.
   flexfec_config->payload_type = recv_flexfec_payload_type_;
-  if (!IsDisabled(call_->trials(), "WebRTC-FlexFEC-03-Advertised") &&
+  if (IsEnabled(call_->trials(), "WebRTC-FlexFEC-03-Advertised") &&
       sp.GetFecFrSsrc(ssrc, &flexfec_config->remote_ssrc)) {
     flexfec_config->protected_media_ssrcs = {ssrc};
     flexfec_config->local_ssrc = config->rtp.local_ssrc;

media/engine/webrtc_video_engine_unittest.cc

@@ -951,36 +951,26 @@ TEST_F(WebRtcVideoEngineTest, SimulcastEnabledForH264BehindFieldTrial) {
   EXPECT_TRUE(channel->SetVideoSend(ssrcs[0], nullptr, nullptr));
 }
 
-// Test that FlexFEC is not supported as a send video codec by default.
+// Test that the FlexFEC field trial properly alters the output of
-// Only enabling field trial should allow advertising FlexFEC send codec.
+// WebRtcVideoEngine::codecs(), for an existing |engine_| object.
-TEST_F(WebRtcVideoEngineTest, Flexfec03SendCodecEnablesWithFieldTrial) {
+//
+// TODO(brandtr): Remove this test, when the FlexFEC field trial is gone.
+TEST_F(WebRtcVideoEngineTest,
+       Flexfec03SupportedAsInternalCodecBehindFieldTrial) {
   encoder_factory_->AddSupportedVideoCodecType("VP8");
 
   auto flexfec = Field("name", &VideoCodec::name, "flexfec-03");
 
+  // FlexFEC is not active without field trial.
   EXPECT_THAT(engine_.send_codecs(), Not(Contains(flexfec)));
 
+  // FlexFEC is active with field trial.
   RTC_DCHECK(!override_field_trials_);
   override_field_trials_ = std::make_unique<webrtc::test::ScopedFieldTrials>(
       "WebRTC-FlexFEC-03-Advertised/Enabled/");
   EXPECT_THAT(engine_.send_codecs(), Contains(flexfec));
 }
 
-// Test that FlexFEC is supported as a receive video codec by default.
-// Disabling field trial should prevent advertising FlexFEC receive codec.
-TEST_F(WebRtcVideoEngineTest, Flexfec03ReceiveCodecDisablesWithFieldTrial) {
-  decoder_factory_->AddSupportedVideoCodecType("VP8");
-
-  auto flexfec = Field("name", &VideoCodec::name, "flexfec-03");
-
-  EXPECT_THAT(engine_.recv_codecs(), Contains(flexfec));
-
-  RTC_DCHECK(!override_field_trials_);
-  override_field_trials_ = std::make_unique<webrtc::test::ScopedFieldTrials>(
-      "WebRTC-FlexFEC-03-Advertised/Disabled/");
-  EXPECT_THAT(engine_.recv_codecs(), Not(Contains(flexfec)));
-}
-
 // Test that codecs are added in the order they are reported from the factory.
 TEST_F(WebRtcVideoEngineTest, ReportSupportedCodecs) {
   encoder_factory_->AddSupportedVideoCodecType("VP8");
@@ -4027,13 +4017,13 @@ TEST_F(WebRtcVideoChannelTest, FlexfecRecvCodecWithoutSsrcNotExposedByDefault) {
   EXPECT_TRUE(streams.empty());
 }
 
-TEST_F(WebRtcVideoChannelTest, FlexfecRecvCodecWithSsrcExposedByDefault) {
+TEST_F(WebRtcVideoChannelTest, FlexfecRecvCodecWithSsrcNotExposedByDefault) {
   AddRecvStream(
       CreatePrimaryWithFecFrStreamParams("cname", kSsrcs1[0], kFlexfecSsrc));
 
   const std::vector<FakeFlexfecReceiveStream*>& streams =
       fake_call_->GetFlexfecReceiveStreams();
-  EXPECT_EQ(1U, streams.size());
+  EXPECT_TRUE(streams.empty());
 }
 
 // TODO(brandtr): When FlexFEC is no longer behind a field trial, merge all

pc/peer_connection_end_to_end_unittest.cc

@@ -21,7 +21,6 @@
 #include "media/sctp/sctp_transport_internal.h"
 #include "rtc_base/gunit.h"
 #include "rtc_base/logging.h"
-#include "test/field_trial.h"
 
 #ifdef WEBRTC_ANDROID
 #include "pc/test/android_test_initializer.h"
@@ -429,11 +428,6 @@ TEST_P(PeerConnectionEndToEndTest, CallWithCustomCodec) {
     std::vector<webrtc::AudioCodecPairId>* const codec_ids_;
   };
 
-  // Disable advertising FlexFEC as receive codec to avoid running out of unique
-  // payload types. See bugs.webrtc.org/12194
-  webrtc::test::ScopedFieldTrials field_trials(
-      "WebRTC-FlexFEC-03-Advertised/Disabled/");
-
   std::vector<webrtc::AudioCodecPairId> encoder_id1, encoder_id2, decoder_id1,
       decoder_id2;
   CreatePcs(rtc::scoped_refptr<webrtc::AudioEncoderFactory>(

pc/peer_connection_integrationtest.cc

@@ -2021,10 +2021,6 @@ TEST_P(PeerConnectionIntegrationTest, EndToEndCallWithSendOnlyVideo) {
 // Tests that receive only works without the caller having an encoder factory
 // and the callee having a decoder factory.
 TEST_P(PeerConnectionIntegrationTest, EndToEndCallWithReceiveOnlyVideo) {
-  // Disable advertising FlexFEC as receive codec to avoid running out of unique
-  // payload types. See bugs.webrtc.org/12194
-  webrtc::test::ScopedFieldTrials field_trials(
-      "WebRTC-FlexFEC-03-Advertised/Disabled/");
   ASSERT_TRUE(
       CreateOneDirectionalPeerConnectionWrappers(/*caller_to_callee=*/false));
   ConnectFakeSignaling();