tray: Show warning in network tray when VPN or proxy used.

ash/mus/system_tray_delegate_mus.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 "ash/mus/system_tray_delegate_mus.h"
 
 #include "ash/session/session_controller.h"
 #include "ash/shell.h"
 #include "ash/system/networking_config_delegate.h"
 
 namespace ash {
 namespace {
 
 // TODO(mash): Provide a real implementation, perhaps by folding its behavior
 // into an ash-side network information cache. http://crbug.com/651157
 class StubNetworkingConfigDelegate : public NetworkingConfigDelegate {
  public:
   StubNetworkingConfigDelegate() {}
   ~StubNetworkingConfigDelegate() override {}
 
  private:
   // NetworkingConfigDelegate:
   std::unique_ptr<const ExtensionInfo> LookUpExtensionForNetwork(
       const std::string& guid) override {
     return nullptr;
   }
 
+  bool HasDefaultNetworkProxyConfigured() override { return false; }
+
   DISALLOW_COPY_AND_ASSIGN(StubNetworkingConfigDelegate);
 };
 
 }  // namespace
 
 SystemTrayDelegateMus::SystemTrayDelegateMus()
     : networking_config_delegate_(new StubNetworkingConfigDelegate) {}
 
 SystemTrayDelegateMus::~SystemTrayDelegateMus() {
 }
 
 LoginStatus SystemTrayDelegateMus::GetUserLoginStatus() const {
   return Shell::Get()->session_controller()->login_status();
 }
 
 NetworkingConfigDelegate* SystemTrayDelegateMus::GetNetworkingConfigDelegate()
     const {
   return networking_config_delegate_.get();
 }
 
 }  // namespace ash