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

net/quic/core/quic_protocol_test.cc

Index: net/quic/core/quic_protocol_test.cc
diff --git a/net/quic/core/quic_protocol_test.cc b/net/quic/core/quic_protocol_test.cc
index 21ea85ff5c6ab1b3cd14f6492af3e0aba04e36fd..3d31b022e64de51724464e6f33945cd412c0cf74 100644
--- a/net/quic/core/quic_protocol_test.cc
+++ b/net/quic/core/quic_protocol_test.cc
@@ -285,12 +285,7 @@ TEST(QuicProtocolTest, PathCloseFrameToString) {
 }
 
 TEST(QuicProtocolTest, FilterSupportedVersions) {
-  ValueRestore<bool> old_v35_flag(&FLAGS_quic_enable_version_35,
-                                  FLAGS_quic_enable_version_35);
-  ValueRestore<bool> old_v36_flag(&FLAGS_quic_enable_version_36,
-                                  FLAGS_quic_enable_version_36);
-  ValueRestore<bool> old_v36_2_flag(&FLAGS_quic_enable_version_36_v2,
-                                    FLAGS_quic_enable_version_36_v2);
+  QuicFlagSaver flags;
   QuicVersionVector all_versions = {
       QUIC_VERSION_30, QUIC_VERSION_31, QUIC_VERSION_32, QUIC_VERSION_33,
       QUIC_VERSION_34, QUIC_VERSION_35, QUIC_VERSION_36};
@@ -307,10 +302,7 @@ TEST(QuicProtocolTest, FilterSupportedVersions) {
 }
 
 TEST(QuicProtocolTest, QuicVersionManager) {
-  ValueRestore<bool> old_v35_flag(&FLAGS_quic_enable_version_35,
-                                  FLAGS_quic_enable_version_35);
-  ValueRestore<bool> old_v36_2_flag(&FLAGS_quic_enable_version_36_v2,
-                                    FLAGS_quic_enable_version_36_v2);
+  QuicFlagSaver flags;
   FLAGS_quic_enable_version_35 = false;
   FLAGS_quic_enable_version_36_v2 = false;
   QuicVersionManager manager(AllSupportedVersions());