Add disable add call during video call extra and carrier config key

Bug: 29047863

Change-Id: I977041ec72968bdccc69a706e27dd4b5ec336ba7
diff --git a/telecomm/java/android/telecom/Connection.java b/telecomm/java/android/telecom/Connection.java
index 2a0a9a6..1b14d65 100644
--- a/telecomm/java/android/telecom/Connection.java
+++ b/telecomm/java/android/telecom/Connection.java
@@ -375,6 +375,14 @@
             "android.telecom.extra.ANSWERING_DROPS_FG_CALL";
 
     /**
+     * Boolean connection extra key on a {@link Connection} which indicates that adding an
+     * additional call is disallowed when there is a video call in progress.
+     * @hide
+     */
+    public static final String EXTRA_DISABLE_ADD_CALL_DURING_VIDEO_CALL =
+            "android.telecom.extra.DISABLE_ADD_CALL_DURING_VIDEO_CALL";
+
+    /**
      * Connection event used to inform Telecom that it should play the on hold tone.  This is used
      * to play a tone when the peer puts the current call on hold.  Sent to Telecom via
      * {@link #sendConnectionEvent(String)}.