QUIC enable server push by default. Guarded by FLAGS_quic_enable_server_push_by_default.

net/quic/core/quic_server_session_base.cc

Index: net/quic/core/quic_server_session_base.cc
diff --git a/net/quic/core/quic_server_session_base.cc b/net/quic/core/quic_server_session_base.cc
index 7cdc014803ea17d0b388d3ae0f61da52dafd520c..419c105042db9734395ec5beda200514f293ea8f 100644
--- a/net/quic/core/quic_server_session_base.cc
+++ b/net/quic/core/quic_server_session_base.cc
@@ -31,8 +31,7 @@ QuicServerSessionBase::QuicServerSessionBase(
       bandwidth_resumption_enabled_(false),
       bandwidth_estimate_sent_to_client_(QuicBandwidth::Zero()),
       last_scup_time_(QuicTime::Zero()),
-      last_scup_packet_number_(0),
-      server_push_enabled_(false) {}
+      last_scup_packet_number_(0) {}
 
 QuicServerSessionBase::~QuicServerSessionBase() {}
 
@@ -56,8 +55,12 @@ void QuicServerSessionBase::OnConfigNegotiated() {
       ContainsQuicTag(config()->ReceivedConnectionOptions(), kBWMX);
   bandwidth_resumption_enabled_ =
       last_bandwidth_resumption || max_bandwidth_resumption;
-  server_push_enabled_ =
-      ContainsQuicTag(config()->ReceivedConnectionOptions(), kSPSH);
+
+  if (!FLAGS_quic_enable_server_push_by_default ||
+      connection()->version() < QUIC_VERSION_35) {
+    set_server_push_enabled(
+        ContainsQuicTag(config()->ReceivedConnectionOptions(), kSPSH));
+  }
 
   // If the client has provided a bandwidth estimate from the same serving
   // region as this server, then decide whether to use the data for bandwidth