Sent PRIORITY_UPDATE frame when priority changes.

gfe-relnote: n/a, change to QUIC v99-only code.  Protected by existing disabled gfe2_reloadable_flag_quic_enable_version_99.
PiperOrigin-RevId: 292458752
Change-Id: I210de2980d1e79d9654ea16fd20ab663200fb2ed
diff --git a/quic/core/quic_stream.cc b/quic/core/quic_stream.cc
index a440a13..bcdf0d9 100644
--- a/quic/core/quic_stream.cc
+++ b/quic/core/quic_stream.cc
@@ -562,6 +562,9 @@
 
 void QuicStream::SetPriority(const spdy::SpdyStreamPrecedence& precedence) {
   precedence_ = precedence;
+
+  MaybeSendPriorityUpdateFrame();
+
   session_->UpdateStreamPriority(id(), precedence);
 }