Adding "wifi only" option for wifi calling.

- Added "wifi-only" option to the list of wifi calling modes.
- Added code in settings initialization to check whether the carrier
supports including the wifi-only option.  If it does not, changes the
entries/values to a ser which does not include the wifi-only option.

Bug: 27858149
Change-Id: Ib02a97afcf6f2722c28b7a4d9c241774944c52d0

src/com/android/settings/WifiCallingSettings.java

@@ -168,12 +168,20 @@ public class WifiCallingSettings extends SettingsPreferenceFragment
 
         CarrierConfigManager configManager = (CarrierConfigManager)
                 getSystemService(Context.CARRIER_CONFIG_SERVICE);
+        boolean isWifiOnlySupported = true;
         if (configManager != null) {
             PersistableBundle b = configManager.getConfig();
             if (b != null) {
                 mEditableWfcMode = b.getBoolean(CarrierConfigManager.KEY_EDITABLE_WFC_MODE_BOOL);
+                isWifiOnlySupported = b.getBoolean(
+                        CarrierConfigManager.KEY_CARRIER_WFC_SUPPORTS_WIFI_ONLY_BOOL, true);
             }
         }
+
+        if (!isWifiOnlySupported) {
+            mButtonWfcMode.setEntries(R.array.wifi_calling_mode_choices_without_wifi_only);
+            mButtonWfcMode.setEntryValues(R.array.wifi_calling_mode_values_without_wifi_only);
+        }
     }
 
     @Override