Add a new QuicFlagSaver class for saving/restoring the values of QUIC flags in tests.

net/quic/core/congestion_control/general_loss_algorithm_test.cc

Index: net/quic/core/congestion_control/general_loss_algorithm_test.cc
diff --git a/net/quic/core/congestion_control/general_loss_algorithm_test.cc b/net/quic/core/congestion_control/general_loss_algorithm_test.cc
index 959112681437393ea49684b1fbb285b0660436d3..fe43cc527aea2120af9812e14f7630e5fd7229e9 100644
--- a/net/quic/core/congestion_control/general_loss_algorithm_test.cc
+++ b/net/quic/core/congestion_control/general_loss_algorithm_test.cc
@@ -11,6 +11,7 @@
 #include "net/quic/core/quic_flags.h"
 #include "net/quic/core/quic_unacked_packet_map.h"
 #include "net/quic/test_tools/mock_clock.h"
+#include "net/quic/test_tools/quic_test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using std::vector;
@@ -58,6 +59,7 @@ class GeneralLossAlgorithmTest : public ::testing::Test {
     }
   }
 
+  QuicFlagSaver flags_;  // Save/restore all QUIC flag values.
   QuicUnackedPacketMap unacked_packets_;
   GeneralLossAlgorithm loss_algorithm_;
   RttStats rtt_stats_;