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

content/browser/loader/network_service_interface.cc

+// 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.
+
+#include "content/browser/loader/network_service_interface.h"
+
+#include "base/lazy_instance.h"
+#include "content/browser/loader/netlog_observer.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+namespace {
+
+NetworkServiceInterface* g_instance;
+
+}  // namespace
+
+NetworkServiceInterface::NetworkServiceInterface() {}
+
+// static
+NetworkServiceInterface* NetworkServiceInterface::GetInstance() {
+  static base::LazyInstance<NetworkServiceInterface>::Leaky instance;
+  return instance.Pointer();
+}
+
+void NetworkServiceInterface::EnableNetLogObserver() {
+  // TODO(scottmg): This should probably keep track of a count.
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&NetLogObserver::Attach));
+}
+
+void NetworkServiceInterface::DisableNetLogObserver() {
+  // TODO(scottmg): This should probably keep track of a count.
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&NetLogObserver::Detach));
+}
+
+}  // namespace content