Introduce SystemNetworkContextManager.

content/public/browser/network_service_instance.h

+// Copyright 2017 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.
+
+#ifndef CONTENT_PUBLIC_BROWSER_NETWORK_SERVICE_INSTANCE_H_
+#define CONTENT_PUBLIC_BROWSER_NETWORK_SERVICE_INSTANCE_H_
+
+#include "content/common/content_export.h"
+
+namespace content {
+
+namespace mojom {
+class NetworkService;
+}
+
+// Returns a pointer to the NetworkService, creating / re-creating it as needed.
+// Must only be called on the UI thread. Must not be called if OOP

[jam, 2017/07/08 01:30:08]

nit: "OOP" unnecessary?

[mmenke, 2017/07/10 15:52:22]

Done.

+// NetworkService is disabled.
+CONTENT_EXPORT mojom::NetworkService* GetNetworkService();

[mmenke, 2017/07/07 20:51:53]

Not sure if there's a better way to do this - basically both chrome/ and
content/ need access to the same mojom::NetworkService, to guarantee that any
initialization chrome/ does is done first.  And chrome/ needs to be able to
access it at all (i.e., can't just have it passed in when creating profiles). 
We could put an accessor in ContentBrowserClient, if we wanted to, though that's
kind of a grab bag of stuff, and it's unclear how we'd grab the service in
Chrome (Maybe have SystemNetworkContextManager own it as well?)

[mmenke, 2017/07/07 20:56:55]

Sorry, that should be "chrome needs to be able to access it on its own"

+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_NETWORK_SERVICE_INSTANCE_H_