Promotes more accessors from WmShell to Shell

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

Index: ash/common/system/chromeos/network/tray_vpn.cc
diff --git a/ash/common/system/chromeos/network/tray_vpn.cc b/ash/common/system/chromeos/network/tray_vpn.cc
index 38379debef143194083eb4cd88a05e824ba2e442..f9ffe1b0ce53f4ec939d93c149b8fc3ce8904434 100644
--- a/ash/common/system/chromeos/network/tray_vpn.cc
+++ b/ash/common/system/chromeos/network/tray_vpn.cc
@@ -45,7 +45,7 @@ class VpnDefaultView : public TrayItemMore,
   static bool ShouldShow() {
     // Show the VPN entry in the ash tray bubble if at least one third-party VPN
     // provider is installed.
-    if (WmShell::Get()->vpn_list()->HaveThirdPartyVPNProviders())
+    if (Shell::Get()->vpn_list()->HaveThirdPartyVPNProviders())
       return true;
 
     // Also show the VPN entry if at least one VPN network is configured.