Remove using namespace in net/quic/quic_stream_sequencer.h

net/tools/quic/quic_server_session_test.cc

Index: net/tools/quic/quic_server_session_test.cc
diff --git a/net/tools/quic/quic_server_session_test.cc b/net/tools/quic/quic_server_session_test.cc
index 4705c05aa0145d34e00f2e222173d420759bfae9..b3910914f3624a03c4e307ee96f59cf1329edf34 100644
--- a/net/tools/quic/quic_server_session_test.cc
+++ b/net/tools/quic/quic_server_session_test.cc
@@ -37,6 +37,7 @@ using net::test::kClientDataStreamId1;
 using net::test::kClientDataStreamId2;
 using net::test::kClientDataStreamId3;
 using net::test::kClientDataStreamId4;
+using std::string;
 using testing::StrictMock;
 using testing::_;