Create scaffolding for experimenting with PCC. Protected by FLAGS_quic_reloadable_flag_quic_enable…

net/quic/core/quic_sent_packet_manager.cc

Index: net/quic/core/quic_sent_packet_manager.cc
diff --git a/net/quic/core/quic_sent_packet_manager.cc b/net/quic/core/quic_sent_packet_manager.cc
index afb8eff9e1226af028512e42312728b3fd62e003..c71b137e25aa1687d9ce12e21f2aead4a5230b8c 100644
--- a/net/quic/core/quic_sent_packet_manager.cc
+++ b/net/quic/core/quic_sent_packet_manager.cc
@@ -117,7 +117,11 @@ void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) {
     }
   } else if (config.HasClientRequestedIndependentOption(kBYTE, perspective_)) {
     SetSendAlgorithm(kCubic);
+  } else if (FLAGS_quic_reloadable_flag_quic_enable_pcc &&
+             config.HasClientRequestedIndependentOption(kTPCC, perspective_)) {
+    SetSendAlgorithm(kPCC);
   }
+
   using_pacing_ = !FLAGS_quic_disable_pacing_for_perf_tests;
 
   if (config.HasClientSentConnectionOption(k1CON, perspective_)) {
@@ -796,9 +800,8 @@ const QuicTime::Delta QuicSentPacketManager::GetTailLossProbeDelay() const {
                  static_cast<int64_t>(0.5 * srtt.ToMilliseconds())));
   }
   if (!unacked_packets_.HasMultipleInFlightPackets()) {
-    return std::max(2 * srtt,
-                    1.5 * srtt + QuicTime::Delta::FromMilliseconds(
-                                     kMinRetransmissionTimeMs / 2));
+    return std::max(2 * srtt, 1.5 * srtt + QuicTime::Delta::FromMilliseconds(
+                                               kMinRetransmissionTimeMs / 2));
   }
   return QuicTime::Delta::FromMilliseconds(
       std::max(kMinTailLossProbeTimeoutMs,