Move DevToolsNetLogObserver to c/b/loader and create stub of network service interface

content/browser/loader/network_service_interface.h

+// Copyright 2016 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_BROWSER_LOADER_NETWORK_SERVICE_INTERFACE_H_
+#define CONTENT_BROWSER_LOADER_NETWORK_SERVICE_INTERFACE_H_
+
+#include "base/macros.h"
+
+namespace content {
+
+// This is a placeholder for what will eventually become a Mojo-exposed
+// interface to the network service. See https://crbug.com/598073.
+class NetworkServiceInterface {
+ public:
+  NetworkServiceInterface();
+
+  static NetworkServiceInterface* GetInstance();
+
+  // APIs available from content-side.
+  void EnableNetLogObserver();
+  void DisableNetLogObserver();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NetworkServiceInterface);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_NETWORK_SERVICE_INTERFACE_H_