Revert "document footgun behavior of codec munging and setCodecPreferences"

This reverts commit e7162754c0229d10c903525be3f900edb184dfb7.

Reason for revert: Breaks downstream project

Original change's description:
> document footgun behavior of codec munging and setCodecPreferences
>
> which drops the munged codec
>
> BUG=webrtc:396344370
>
> Change-Id: I4980c6980ad7df29d4d1451777a61f90dac73f74
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/389440
> Reviewed-by: Evan Shrubsole <eshr@webrtc.org>
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Commit-Queue: Philipp Hancke <phancke@meta.com>
> Cr-Commit-Position: refs/heads/main@{#44555}

Bug: webrtc:396344370
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I86e7929217420bf4f1741910e628430b660d4418
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/390660
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Auto-Submit: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Evan Shrubsole <eshr@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#44560}

pc/peer_connection_integrationtest.cc

diff --git a/pc/peer_connection_integrationtest.cc b/pc/peer_connection_integrationtest.cc
index a3e9750..95bd835 100644
--- a/pc/peer_connection_integrationtest.cc
+++ b/pc/peer_connection_integrationtest.cc
@@ -18,7 +18,6 @@
 #include <stdint.h>
 
 #include <algorithm>
-#include <cstddef>
 #include <memory>
 #include <optional>
 #include <string>
@@ -4795,99 +4794,6 @@
 }
 
 TEST_F(PeerConnectionIntegrationTestUnifiedPlan,
-       MungeOfferCodecAndReOfferWorksWithSetCodecPreferencesIsAFootgun) {
-  ASSERT_TRUE(CreatePeerConnectionWrappers());
-  ConnectFakeSignaling();
-  caller()->AddVideoTrack();
-  auto munger = [](std::unique_ptr<SessionDescriptionInterface>& sdp) {
-    auto video = GetFirstVideoContentDescription(sdp->description());
-    auto codecs = video->codecs();
-    std::optional<Codec> replacement_codec;
-    for (auto&& codec : codecs) {
-      if (codec.name == "AV1") {
-        replacement_codec = codec;
-        break;
-      }
-    }
-    if (replacement_codec) {
-      for (auto&& codec : codecs) {
-        if (codec.name == "VP8") {
-          RTC_LOG(LS_INFO) << "Remapping VP8 codec " << codec << " to AV1";
-          codec.name = replacement_codec->name;
-          codec.params = replacement_codec->params;
-          break;
-        }
-      }
-      video->set_codecs(codecs);
-    } else {
-      RTC_LOG(LS_INFO) << "Skipping munge, no AV1 codec found";
-    }
-  };
-  caller()->SetGeneratedSdpMunger(munger);
-  caller()->CreateAndSetAndSignalOffer();
-  ASSERT_THAT(
-      WaitUntil([&] { return SignalingStateStable(); }, ::testing::IsTrue()),
-      IsRtcOk());
-  caller()->SetGeneratedSdpMunger(nullptr);
-
-  // Note currently negotiated codecs and count VP9 and AV1.
-  auto codecs_after_munge = caller()
-                                ->pc()
-                                ->local_description()
-                                ->description()
-                                ->contents()[0]
-                                .media_description()
-                                ->codecs();
-  size_t av1_munge = 0;
-  size_t vp8_munge = 0;
-  for (const auto& codec : codecs_after_munge) {
-    if (codec.name == "AV1")
-      av1_munge++;
-    else if (codec.name == "VP8")
-      vp8_munge++;
-  }
-  // We should have replaced VP8 with AV1.
-  EXPECT_EQ(av1_munge, 2u);
-  EXPECT_EQ(vp8_munge, 0u);
-
-  // Call setCodecPreferences.
-  std::vector<RtpCodecCapability> codecs =
-      caller()
-          ->pc_factory()
-          ->GetRtpReceiverCapabilities(webrtc::MediaType::VIDEO)
-          .codecs;
-  auto transceivers = caller()->pc()->GetTransceivers();
-  ASSERT_EQ(transceivers.size(), 1u);
-  transceivers[0]->SetCodecPreferences(codecs);
-
-  auto offer = caller()->CreateOfferAndWait();
-  ASSERT_NE(offer, nullptr);
-  // The offer should be acceptable.
-  EXPECT_TRUE(caller()->SetLocalDescriptionAndSendSdpMessage(std::move(offer)));
-
-  auto codecs_after_scp = caller()
-                              ->pc()
-                              ->local_description()
-                              ->description()
-                              ->contents()[0]
-                              .media_description()
-                              ->codecs();
-  size_t av1_scp = 0;
-  size_t vp8_scp = 0;
-  for (const auto& codec : codecs_after_scp) {
-    if (codec.name == "AV1")
-      av1_scp++;
-    else if (codec.name == "VP8")
-      vp8_scp++;
-  }
-  // The SDP munging modification was reverted by sCP.
-  // This is a footgun but please do not mix such munging with
-  // setCodecPreferences, munging is on the way out.
-  EXPECT_EQ(av1_scp, 1u);
-  EXPECT_EQ(vp8_scp, 1u);
-}
-
-TEST_F(PeerConnectionIntegrationTestUnifiedPlan,
        SensibleRtxWithDuplicateCodecs) {
   ASSERT_TRUE(CreatePeerConnectionWrappers());
   caller()->AddVideoTrack();
@@ -4931,7 +4837,7 @@
   // associated RTX codec.
   std::unique_ptr<SessionDescriptionInterface> answer =
       caller()->CreateAnswerForTest();
-  ASSERT_NE(answer, nullptr);
+  ASSERT_THAT(answer, NotNull());
   RTC_LOG(LS_ERROR) << "Answer is " << *answer;
   ASSERT_THAT(answer->description()->contents().size(), Eq(1));
   auto codecs =
@@ -4990,7 +4896,7 @@
   caller()->AddVideoTrack();
   auto offer2 = caller()->CreateOfferAndWait();
   // Observe that packetization is raw on BOTH media sections.
-  ASSERT_NE(offer2, nullptr);
+  ASSERT_THAT(offer2, NotNull());
   EXPECT_EQ(offer2->description()->contents().size(), 2U);
   for (const auto& content : offer2->description()->contents()) {
     for (const auto& codec : content.media_description()->codecs()) {