[AT&T] Add key to show 4g for 3g RAT.

This key is introduced for AT&T

This will also require a carrier-config side change
to set show_4g_for_3g_data_icon_bool to true.

This will replace H/H+ that is shown by AT&T today.

Bug: 138655095
Test: manually

Change-Id: I480e14be41f8edbe607472351efd39d6d91b81b0
diff --git a/telephony/java/android/telephony/CarrierConfigManager.java b/telephony/java/android/telephony/CarrierConfigManager.java
index 56a6d61..4ba2614 100755
--- a/telephony/java/android/telephony/CarrierConfigManager.java
+++ b/telephony/java/android/telephony/CarrierConfigManager.java
@@ -1405,6 +1405,13 @@
             "show_4g_for_lte_data_icon_bool";
 
     /**
+     * Boolean indicating if default data account should show 4G icon when in 3G.
+     * @hide
+     */
+    public static final String KEY_SHOW_4G_FOR_3G_DATA_ICON_BOOL =
+            "show_4g_for_3g_data_icon_bool";
+
+    /**
      * Boolean indicating if lte+ icon should be shown if available
      * @hide
      */
@@ -3383,6 +3390,7 @@
         sDefaults.putBoolean(KEY_SPN_DISPLAY_RULE_USE_ROAMING_FROM_SERVICE_STATE_BOOL, false);
         sDefaults.putBoolean(KEY_ALWAYS_SHOW_DATA_RAT_ICON_BOOL, false);
         sDefaults.putBoolean(KEY_SHOW_4G_FOR_LTE_DATA_ICON_BOOL, false);
+        sDefaults.putBoolean(KEY_SHOW_4G_FOR_3G_DATA_ICON_BOOL, false);
         sDefaults.putString(KEY_OPERATOR_NAME_FILTER_PATTERN_STRING, "");
         sDefaults.putString(KEY_SHOW_CARRIER_DATA_ICON_PATTERN_STRING, "");
         sDefaults.putBoolean(KEY_HIDE_LTE_PLUS_DATA_ICON_BOOL, true);