chromeos: Move ownership of ash VPN provider list from chrome into ash

ash/mus/vpn_delegate_mus.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 ASH_MUS_VPN_DELEGATE_MUS_H_
 #define ASH_MUS_VPN_DELEGATE_MUS_H_
 
 #include "ash/common/system/chromeos/network/vpn_delegate.h"
 #include "base/macros.h"
 
 namespace ash {
 
 // VPN delegate for mustash. Fetches VPN data from browser process over mojo.
 class VPNDelegateMus : public VPNDelegate {
  public:
   VPNDelegateMus();
   ~VPNDelegateMus() override;
 
  private:
   // VPNDelegate:
-  bool HaveThirdPartyVPNProviders() const override;
-  const std::vector<VPNProvider>& GetVPNProviders() const override;
-  void ShowAddPage(const VPNProvider::Key& key) override;
-
-  // GetVPNProviders returns a reference to this list.
-  std::vector<VPNProvider> providers_;
+  void ShowAddPage(const std::string& extension_id) override;
 
   DISALLOW_COPY_AND_ASSIGN(VPNDelegateMus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_MUS_VPN_DELEGATE_MUS_H_