Ims: Add support to add participants to existing call

Supports initiation of a conference call
by directly adding participants to existing call

Test: Manual
Bug: 62151032
Change-Id: I4e60efafab4761ae65a460fdc6c4cacc3e233220

telecomm/java/android/telecom/InCallAdapter.java

@@ -282,6 +282,20 @@ public final class InCallAdapter {
         }
     }
 
+    /**
+     * Instructs Telecom to pull participants to existing call
+     *
+     * @param callId The unique ID of the call.
+     * @param participants participants to be pulled to existing call.
+     */
+    public void addConferenceParticipants(String callId, List<Uri> participants) {
+        try {
+            mAdapter.addConferenceParticipants(callId, participants);
+        } catch (RemoteException ignored) {
+        }
+    }
+
+
     /**
      * Instructs Telecom to split the specified call from any conference call with which it may be
      * connected.