[net/http auth] Use strings to identify authentication schemes.

net/http/http_auth_scheme_set.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/http/http_auth.h"
+#include "net/http/http_auth_scheme_set.h"
+#include "net/http/http_util.h"
+
+namespace net {
+
+HttpAuthSchemeSet::HttpAuthSchemeSet() {}
+
+HttpAuthSchemeSet::~HttpAuthSchemeSet() {}
+
+void HttpAuthSchemeSet::Add(const std::string& scheme) {
+  DCHECK(HttpAuth::IsValidNormalizedScheme(scheme));
+  schemes_.insert(scheme);
+}
+
+bool HttpAuthSchemeSet::Contains(const std::string& scheme) const {
+  DCHECK(HttpAuth::IsValidNormalizedScheme(scheme));
+  auto iter = schemes_.find(scheme);
+  return iter != schemes_.end();
+}
+
+}  // namespace