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

ash/common/system/chromeos/network/vpn_list_view.cc

Index: ash/common/system/chromeos/network/vpn_list_view.cc
diff --git a/ash/common/system/chromeos/network/vpn_list_view.cc b/ash/common/system/chromeos/network/vpn_list_view.cc
index 938a9bd5be588501ea4d741816f2522ee5b366c3..9baee1e1f106c91da8aecd8eb65dcf4bdc8b05ab 100644
--- a/ash/common/system/chromeos/network/vpn_list_view.cc
+++ b/ash/common/system/chromeos/network/vpn_list_view.cc
@@ -472,10 +472,8 @@ void VPNListView::AddProviderAndNetworks(
 void VPNListView::AddProvidersAndNetworks(
     const chromeos::NetworkStateHandler::NetworkStateList& networks) {
   // Get the list of VPN providers enabled in the primary user's profile.
-  std::vector<VPNProvider> providers = WmShell::Get()
-                                           ->system_tray_delegate()
-                                           ->GetVPNDelegate()
-                                           ->GetVPNProviders();
+  std::vector<VPNProvider> providers =
+      WmShell::Get()->system_tray_delegate()->GetVPNDelegate()->vpn_providers();
 
   // Add providers with at least one configured network along with their
   // networks. Providers are added in the order of their highest priority