Guard HTTP/3 priority code behind protocol flag quic_allow_http3_priority which is default false.

gfe-relnote: v99 only, not protected.
PiperOrigin-RevId: 269610032
Change-Id: Ie15cca2d45ab4821e253cec1f34e6e513fde5165
diff --git a/quic/core/http/quic_spdy_stream_test.cc b/quic/core/http/quic_spdy_stream_test.cc
index 5db0263..b1f6672 100644
--- a/quic/core/http/quic_spdy_stream_test.cc
+++ b/quic/core/http/quic_spdy_stream_test.cc
@@ -1221,6 +1221,7 @@
 }
 
 TEST_P(QuicSpdyStreamTest, ClientWritesPriority) {
+  SetQuicFlag(FLAGS_quic_allow_http3_priority, true);
   InitializeWithPerspective(kShouldProcessData, Perspective::IS_CLIENT);
 
   if (VersionUsesQpack(GetParam().transport_version)) {