Check callback is run in QuicChromiumClientSession's destructor

net/quic/chromium/quic_chromium_client_session.cc

Index: net/quic/chromium/quic_chromium_client_session.cc
diff --git a/net/quic/chromium/quic_chromium_client_session.cc b/net/quic/chromium/quic_chromium_client_session.cc
index 1dbabc066c5765c65d9bce8231bd6fe8b13a2e3a..607f13b099f71a3bb2cc6487290d5194f81c8ea8 100644
--- a/net/quic/chromium/quic_chromium_client_session.cc
+++ b/net/quic/chromium/quic_chromium_client_session.cc
@@ -298,6 +298,8 @@ QuicChromiumClientSession::QuicChromiumClientSession(
 }
 
 QuicChromiumClientSession::~QuicChromiumClientSession() {
+  DCHECK(callback_.is_null());
+
   net_log_.EndEvent(NetLogEventType::QUIC_SESSION);
   if (!dynamic_streams().empty())
     RecordUnexpectedOpenStreams(DESTRUCTOR);