Support for treating single party IMS conference as a standalone call.

Adding @hide APIs which Telephony can use to make a conference call with
a single participant look like its a standalone call.

Test: Manual testing
Bug: 75975913
Change-Id: Id8532234ab295785fc749b120898f43911e12637
diff --git a/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java b/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java
index 78d65e6..f99b218 100644
--- a/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java
+++ b/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java
@@ -74,6 +74,7 @@
     private static final int MSG_ON_RTT_UPGRADE_REQUEST = 33;
     private static final int MSG_SET_PHONE_ACCOUNT_CHANGED = 34;
     private static final int MSG_CONNECTION_SERVICE_FOCUS_RELEASED = 35;
+    private static final int MSG_SET_CONFERENCE_STATE = 36;
 
     private final IConnectionServiceAdapter mDelegate;
 
@@ -333,6 +334,14 @@
                 case MSG_CONNECTION_SERVICE_FOCUS_RELEASED:
                     mDelegate.onConnectionServiceFocusReleased(null /*Session.Info*/);
                     break;
+                case MSG_SET_CONFERENCE_STATE:
+                    SomeArgs args = (SomeArgs) msg.obj;
+                    try {
+                        mDelegate.setConferenceState((String) args.arg1, (Boolean) args.arg2,
+                                (Session.Info) args.arg3);
+                    } finally {
+                        args.recycle();
+                    }
             }
         }
     };
@@ -615,6 +624,16 @@
         public void resetConnectionTime(String callId, Session.Info sessionInfo) {
             // Do nothing
         }
+
+        @Override
+        public void setConferenceState(String callId, boolean isConference,
+                Session.Info sessionInfo) {
+            SomeArgs args = SomeArgs.obtain();
+            args.arg1 = callId;
+            args.arg2 = isConference;
+            args.arg3 = sessionInfo;
+            mHandler.obtainMessage(MSG_SET_CONFERENCE_STATE, args).sendToTarget();
+        }
     };
 
     public ConnectionServiceAdapterServant(IConnectionServiceAdapter delegate) {