IMS: Allow VT calls when tty-on

- Few operators are not supporting VT calls when TTY settings are ON
- This behavior is due to telephony not allowing VT calls when TTY ON
- Added carrier config based check to allow VT calls for certain operators
- will support both MO VT and VoLTE to VT upgrade functions

Change-Id: I6f0ed7a1b078b4e7fe31fd969784b4748ce2ab0b
CRs-Fixed: 2771977
diff --git a/telephony/java/android/telephony/CarrierConfigManager.java b/telephony/java/android/telephony/CarrierConfigManager.java
index 76d552a..02b1b4c 100644
--- a/telephony/java/android/telephony/CarrierConfigManager.java
+++ b/telephony/java/android/telephony/CarrierConfigManager.java
@@ -816,6 +816,13 @@
     public static final String KEY_CARRIER_VOLTE_TTY_SUPPORTED_BOOL
             = "carrier_volte_tty_supported_bool";
 
+     /**
+     * Flag indicating whether VT tty is supported
+     * @hide
+     */
+    public static final String KEY_CARRIER_VT_TTY_SUPPORT_BOOL =
+            "carrier_vt_tty_support_bool";
+
     /**
      * Flag specifying whether IMS service can be turned off. If false then the service will not be
      * turned-off completely, but individual features can be disabled.
@@ -3916,6 +3923,7 @@
         sDefaults.putBoolean(KEY_CARRIER_SUPPORTS_SS_OVER_UT_BOOL, false);
         sDefaults.putBoolean(KEY_CARRIER_VOLTE_OVERRIDE_WFC_PROVISIONING_BOOL, false);
         sDefaults.putBoolean(KEY_CARRIER_VOLTE_TTY_SUPPORTED_BOOL, true);
+        sDefaults.putBoolean(KEY_CARRIER_VT_TTY_SUPPORT_BOOL, false);
         sDefaults.putBoolean(KEY_CARRIER_ALLOW_TURNOFF_IMS_BOOL, true);
         sDefaults.putBoolean(KEY_CARRIER_IMS_GBA_REQUIRED_BOOL, false);
         sDefaults.putBoolean(KEY_CARRIER_INSTANT_LETTERING_AVAILABLE_BOOL, false);