Instead of immediate data flush, always try to bundle QPACK decoder data opportunistically.

This change is based on Bence's cl/553795731.

Protected by FLAGS_quic_restart_flag_quic_opport_bundle_qpack_decoder_data.

PiperOrigin-RevId: 557313748
diff --git a/quiche/quic/core/quic_connection_test.cc b/quiche/quic/core/quic_connection_test.cc
index daa49b3..ccb65bf 100644
--- a/quiche/quic/core/quic_connection_test.cc
+++ b/quiche/quic/core/quic_connection_test.cc
@@ -700,6 +700,9 @@
     EXPECT_CALL(visitor_, OnCongestionWindowChange(_)).Times(AnyNumber());
     EXPECT_CALL(visitor_, OnPacketReceived(_, _, _)).Times(AnyNumber());
     EXPECT_CALL(visitor_, OnSuccessfulVersionNegotiation(_)).Times(AnyNumber());
+    if (GetQuicRestartFlag(quic_opport_bundle_qpack_decoder_data)) {
+      EXPECT_CALL(visitor_, MaybeBundleOpportunistically()).Times(AnyNumber());
+    }
     EXPECT_CALL(visitor_, OnOneRttPacketAcknowledged())
         .Times(testing::AtMost(1));
     EXPECT_CALL(*loss_algorithm_, GetLossTimeout())