Remove using namespace in net/quic/quic_stream_sequencer.h

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index 897d2aa18209004304be365e7455e6eb506abc56..387d863ab4b84c9fcd1229ca57596f578c932730 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -178,7 +178,7 @@ class IOThread : public content::BrowserThreadDelegate {
     Optional<bool> enable_spdy_ping_based_connection_checking;
     Optional<net::NextProto> spdy_default_protocol;
     net::NextProtoVector next_protos;
-    Optional<string> trusted_spdy_proxy;
+    Optional<std::string> trusted_spdy_proxy;
     Optional<bool> force_spdy_over_ssl;
     Optional<bool> force_spdy_always;
     std::set<net::HostPortPair> forced_spdy_exclusions;