Create a QUIC wrapper around a mutex and a mutex lock.

net/tools/quic/test_tools/packet_dropping_test_writer.cc

Index: net/tools/quic/test_tools/packet_dropping_test_writer.cc
diff --git a/net/tools/quic/test_tools/packet_dropping_test_writer.cc b/net/tools/quic/test_tools/packet_dropping_test_writer.cc
index 46c2a1a0ea73061885e84186cd599273300e88c6..df1057a1e603023a5c4196d70d7a9bcbbc919e24 100644
--- a/net/tools/quic/test_tools/packet_dropping_test_writer.cc
+++ b/net/tools/quic/test_tools/packet_dropping_test_writer.cc
@@ -84,7 +84,7 @@ WriteResult PacketDroppingTestWriter::WritePacket(
   ++num_calls_to_write_;
   ReleaseOldPackets();
 
-  base::AutoLock locked(config_mutex_);
+  QuicReaderMutexLock lock(&config_mutex_);
   if (fake_drop_first_n_packets_ > 0 &&
       num_calls_to_write_ <=
           static_cast<uint64_t>(fake_drop_first_n_packets_)) {
@@ -168,7 +168,7 @@ QuicTime PacketDroppingTestWriter::ReleaseNextPacket() {
   if (delayed_packets_.empty()) {
     return QuicTime::Zero();
   }
-  base::AutoLock locked(config_mutex_);
+  QuicReaderMutexLock lock(&config_mutex_);
   DelayedPacketList::iterator iter = delayed_packets_.begin();
   // Determine if we should re-order.
   if (delayed_packets_.size() > 1 && fake_packet_reorder_percentage_ > 0 &&