Add disconnect message constant

Bug: b/171255813
Test: make
Change-Id: Ia300b12ecf7d0c1d7d057b48a801b2928354315e

telecomm/java/android/telecom/TelecomManager.java

@@ -371,6 +371,14 @@ public class TelecomManager {
     public static final String EXTRA_CALL_DISCONNECT_MESSAGE =
             "android.telecom.extra.CALL_DISCONNECT_MESSAGE";
 
+    /**
+     * A string value for {@link #EXTRA_CALL_DISCONNECT_MESSAGE}, indicates the call was dropped by
+     * lower layers
+     * @hide
+     */
+    public static final String CALL_AUTO_DISCONNECT_MESSAGE_STRING =
+            "Call dropped by lower layers";
+
     /**
      * Optional extra for {@link android.telephony.TelephonyManager#ACTION_PHONE_STATE_CHANGED}
      * containing the component name of the associated connection service.