Provide mutable members of UrlRequestContext via pure-virtual interface

net/url_request/const_http_user_agent_settings.cc

Index: net/url_request/const_http_user_agent_settings.cc
diff --git a/net/url_request/const_http_user_agent_settings.cc b/net/url_request/const_http_user_agent_settings.cc
new file mode 100644
index 0000000000000000000000000000000000000000..245b02561649da6bcb99cb9dc46f2f3243938076
--- /dev/null
+++ b/net/url_request/const_http_user_agent_settings.cc
@@ -0,0 +1,22 @@
+// Copyright (c) 2012 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/url_request/const_http_user_agent_settings.h"
+
+namespace net {
+
+ConstHttpUserAgentSettings::ConstHttpUserAgentSettings(
+    const std::string& accept_language,
+    const std::string& accept_charset,
+    const std::string& user_agent)
+    : ConstHttpAcceptLanguageAndCharset(accept_language, accept_charset),
+      user_agent_(user_agent) {
+}
+
+std::string ConstHttpUserAgentSettings::GetUserAgent(const GURL& url) {
+  return user_agent_;
+}
+
+}  // namespace net
+