Fix version manager that flip flag in-flight does not make supported versions change.

net/quic/core/quic_protocol.cc

Index: net/quic/core/quic_protocol.cc
diff --git a/net/quic/core/quic_protocol.cc b/net/quic/core/quic_protocol.cc
index 0faea1a367c9fecdb69ada63e5fef4abe78ad484..b074cd1a36689449c7865f64187fe26d473c88b0 100644
--- a/net/quic/core/quic_protocol.cc
+++ b/net/quic/core/quic_protocol.cc
@@ -618,12 +618,20 @@ QuicVersionManager::QuicVersionManager(QuicVersionVector supported_versions)
 QuicVersionManager::~QuicVersionManager() {}
 
 const QuicVersionVector& QuicVersionManager::GetSupportedVersions() {
+  MaybeRefilterSupportedVersions();
+  return filtered_supported_versions_;
+}
+
+void QuicVersionManager::MaybeRefilterSupportedVersions() {
   if (enable_version_36_ != FLAGS_quic_enable_version_36_v3) {
     enable_version_36_ = FLAGS_quic_enable_version_36_v3;
-    filtered_supported_versions_ =
-        FilterSupportedVersions(allowed_supported_versions_);
+    RefilterSupportedVersions();
   }
-  return filtered_supported_versions_;
+}
+
+void QuicVersionManager::RefilterSupportedVersions() {
+  filtered_supported_versions_ =
+      FilterSupportedVersions(allowed_supported_versions_);
 }
 
 AckListenerWrapper::AckListenerWrapper(QuicAckListenerInterface* listener,