Move navigations with POST or referrer to the shell.

mojo/common/user_agent.cc

Index: mojo/common/user_agent.cc
diff --git a/mojo/common/user_agent.cc b/mojo/common/user_agent.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4474e6587726bfceba1109a83edb86eaaa8c1cf6
--- /dev/null
+++ b/mojo/common/user_agent.cc
@@ -0,0 +1,17 @@
+// 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 "mojo/common/user_agent.h"
+
+namespace mojo {
+namespace common {
+
+std::string GetUserAgent() {
+  // TODO(jam): change depending on OS
+  return "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like "
+         "Gecko) Chrome/42.0.2311.68 Safari/537.36";
+}
+
+}  // namespace common
+}  // namespace mojo