Remove special handling of -1 in bandwidth modifiers

This is nonstandard, and appears unused.

Bug: webrtc:502249086
Change-Id: I5b35b43e8ca1d55802e377511d6afa151459bbe4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/485820
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48095}

api/webrtc_sdp.cc

diff --git a/api/webrtc_sdp.cc b/api/webrtc_sdp.cc
index 42e0650..895a5cb 100644
--- a/api/webrtc_sdp.cc
+++ b/api/webrtc_sdp.cc
@@ -2700,9 +2700,7 @@
         ReportSdpBandwidth(kSdpBandwidthParseFailure);
         return false;
       }
-      if (b == -1) {
-        ReportSdpBandwidth(kSdpBandwidthNegativeOne);
-      } else if (b == 0) {
+      if (b == 0) {
         ReportSdpBandwidth(kSdpBandwidthZero);
       } else if (b > 0 && b <= INT_MAX / 1000) {
         ReportSdpBandwidth(kSdpBandwidthSmall);
@@ -2711,16 +2709,6 @@
       } else {
         ReportSdpBandwidth(kSdpBandwidthNegative);
       }
-      // TODO(deadbeef): Historically, applications may be setting a value
-      // of -1 to mean "unset any previously set bandwidth limit", even
-      // though ommitting the "b=AS" entirely will do just that. Once we've
-      // transitioned applications to doing the right thing, it would be
-      // better to treat this as a hard error instead of just ignoring it.
-      if (bandwidth_type == kApplicationSpecificBandwidth && b == -1) {
-        RTC_LOG(LS_WARNING) << "Ignoring \"b=AS:-1\"; will be treated as \"no "
-                               "bandwidth limit\".";
-        continue;
-      }
       if (b < 0) {
         return ParseFailed(
             *line, "b=" + bandwidth_type + " value can't be negative.", error);

api/webrtc_sdp_unittest.cc

diff --git a/api/webrtc_sdp_unittest.cc b/api/webrtc_sdp_unittest.cc
index eb3a1d1..f1cf117 100644
--- a/api/webrtc_sdp_unittest.cc
+++ b/api/webrtc_sdp_unittest.cc
@@ -4021,29 +4021,6 @@
   ExpectParseFailure(std::string(kSdpWithNegativeBandwidth), "b=AS:-1000");
 }
 
-// An exception to the above rule: a value of -1 for b=AS should just be
-// ignored, resulting in "kAutoBandwidth" in the deserialized object.
-// Applications historically may be using "b=AS:-1" to mean "no bandwidth
-// limit", but this is now what ommitting the attribute entirely will do, so
-// ignoring it will have the intended effect.
-TEST_F(WebRtcSdpTest, BandwidthLimitOfNegativeOneIgnored) {
-  static const char kSdpWithBandwidthOfNegativeOne[] =
-      "v=0\r\n"
-      "o=- 18446744069414584320 18446462598732840960 IN IP4 127.0.0.1\r\n"
-      "s=-\r\n"
-      "t=0 0\r\n"
-      "m=video 3457 RTP/SAVPF 120\r\n"
-      "b=AS:-1\r\n";
-
-  std::unique_ptr<SessionDescriptionInterface> jdesc_output =
-      SdpDeserialize(kSdpWithBandwidthOfNegativeOne);
-  ASSERT_THAT(jdesc_output, NotNull());
-  const VideoContentDescription* vcd =
-      GetFirstVideoContentDescription(jdesc_output->description());
-  ASSERT_THAT(vcd, NotNull());
-  EXPECT_EQ(kAutoBandwidth, vcd->bandwidth());
-}
-
 TEST_F(WebRtcSdpTest, SdpBandwidthMetrics) {
   metrics::Reset();
   auto get_sdp = [](absl::string_view value) {
@@ -4057,10 +4034,11 @@
     return sb.Release();
   };
 
-  // kSdpBandwidthNegativeOne
+  // This used to be kSdpBandwidthNegativeOne, but special
+  // treatment is removed.
   SdpDeserialize(get_sdp("-1"));
   EXPECT_METRIC_EQ(1, metrics::NumEvents("WebRTC.PeerConnection.SdpBandwidth",
-                                         kSdpBandwidthNegativeOne));
+                                         kSdpBandwidthNegative));
 
   // kSdpBandwidthZero
   SdpDeserialize(get_sdp("0"));
@@ -4079,7 +4057,7 @@
 
   // kSdpBandwidthNegative
   SdpDeserialize(get_sdp("-1000"));
-  EXPECT_METRIC_EQ(1, metrics::NumEvents("WebRTC.PeerConnection.SdpBandwidth",
+  EXPECT_METRIC_EQ(2, metrics::NumEvents("WebRTC.PeerConnection.SdpBandwidth",
                                          kSdpBandwidthNegative));
 
   // kSdpBandwidthParseFailure