Improve hard-coded QuicSimpleServerStream's push promise id.

In IETF world, HTTP/3 static unidirectional streams are not guaranteed to be created at initialization. So we need to explicitly adjust highest_push_promise_id_ when a new H/3 static stream is created.

gfe-relnote: v99 change only, not protected.
PiperOrigin-RevId: 262976660
Change-Id: I3182356ae6560486b5677abdc73846f452598b24
diff --git a/quic/core/http/quic_spdy_session.h b/quic/core/http/quic_spdy_session.h
index 1f94a79..68becb6 100644
--- a/quic/core/http/quic_spdy_session.h
+++ b/quic/core/http/quic_spdy_session.h
@@ -249,6 +249,9 @@
     return receive_control_stream_;
   }
 
+  // Initializes HTTP/3 unidirectional streams if not yet initialzed.
+  virtual void MaybeInitializeHttp3UnidirectionalStreams();
+
  private:
   friend class test::QuicSpdySessionPeer;
 
@@ -266,9 +269,6 @@
   void OnPriority(spdy::SpdyStreamId stream_id,
                   const spdy::SpdyStreamPrecedence& precedence);
 
-  // Initializes HTTP/3 unidirectional streams if not yet initialzed.
-  void MaybeInitializeHttp3UnidirectionalStreams();
-
   std::unique_ptr<QpackEncoder> qpack_encoder_;
   std::unique_ptr<QpackDecoder> qpack_decoder_;