[cros] Add network tray item for mobile network setup.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index e985684a391648295279158ff07ee076c64e93f0..36b908317a1a4dd2642551b01d76ca2fd9bc33fe 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -471,11 +471,12 @@ class DummySystemTrayDelegate : public SystemTrayDelegate {
   }
 
   virtual bool GetCellularCarrierInfo(std::string* carrier_id,
-                                      std::string* toup_url) OVERRIDE {
+                                      std::string* topup_url,
+                                      std::string* setup_url) OVERRIDE {
     return false;
   }
 
-  virtual void ShowCellularTopupURL(const std::string& topup_url) OVERRIDE {
+  virtual void ShowCellularURL(const std::string& url) OVERRIDE {
   }
 
   virtual void ChangeProxySettings() OVERRIDE {