gfe-relnote: Change error code sent on unknown unidirectional stream type.  Protected by gfe2_reloadable_flag_quic_enable_version_draft_25_v3 and gfe2_reloadable_flag_quic_enable_version_draft_27.

From
https://quicwg.org/base-drafts/draft-ietf-quic-http.html#name-unidirectional-streams:
"Recipients of unknown stream types MAY abort reading of the stream with an
error code of H3_STREAM_CREATION_ERROR"

This CL changes the error code sent from 0xd to 0x103.

PiperOrigin-RevId: 300521130
Change-Id: I11843f7342c8aee0ce9c012e5fab631ee9a31df2

quic/core/http/quic_spdy_session.cc

diff --git a/quic/core/http/quic_spdy_session.cc b/quic/core/http/quic_spdy_session.cc
index e46ea5d..c8d28c1 100644
--- a/quic/core/http/quic_spdy_session.cc
+++ b/quic/core/http/quic_spdy_session.cc
@@ -57,9 +57,6 @@
 #define ENDPOINT \
   (perspective() == Perspective::IS_SERVER ? "Server: " : "Client: ")
 
-// TODO(b/124216424): remove this once HTTP/3 error codes are adopted.
-const uint16_t kHttpUnknownStreamType = 0x0D;
-
 class HeaderTableDebugVisitor : public HpackHeaderTable::DebugVisitorInterface {
  public:
   HeaderTableDebugVisitor(const QuicClock* clock,
@@ -1109,7 +1106,10 @@
       return true;
     }
     default:
-      SendStopSending(kHttpUnknownStreamType, pending->id());
+      SendStopSending(
+          static_cast<QuicApplicationErrorCode>(
+              QuicHttp3ErrorCode::IETF_QUIC_HTTP3_STREAM_CREATION_ERROR),
+          pending->id());
       pending->StopReading();
   }
   return false;

quic/core/http/quic_spdy_session_test.cc

diff --git a/quic/core/http/quic_spdy_session_test.cc b/quic/core/http/quic_spdy_session_test.cc
index bd62260..c0a1269 100644
--- a/quic/core/http/quic_spdy_session_test.cc
+++ b/quic/core/http/quic_spdy_session_test.cc
@@ -2227,7 +2227,17 @@
 
     // A STOP_SENDING frame is sent in response to the unknown stream type.
     EXPECT_CALL(*connection_, SendControlFrame(_))
-        .WillOnce(Invoke(&VerifyAndClearStopSendingFrame));
+        .WillOnce(Invoke([stream_id](const QuicFrame& frame) {
+          EXPECT_EQ(STOP_SENDING_FRAME, frame.type);
+
+          QuicStopSendingFrame* stop_sending = frame.stop_sending_frame;
+          EXPECT_EQ(stream_id, stop_sending->stream_id);
+          EXPECT_EQ(QuicHttp3ErrorCode::IETF_QUIC_HTTP3_STREAM_CREATION_ERROR,
+                    static_cast<QuicHttp3ErrorCode>(
+                        stop_sending->application_error_code));
+
+          return ClearControlFrame(frame);
+        }));
     session_.OnStreamFrame(frame);
 
     PendingStream* pending =