Add further Connection-side APIs for RTT (part 2)

Add methods and callbacks to facilitate local and remote RTT initiation
and termination in the middle of a call. Adds @hide Connection-side APIs
to communicate with the ConnectionService, as well as plumbing for
RemoteConnections.

Test: manual, through telecom testapps
Change-Id: Ia80604b7dff8586ff222dbccdbe55e91aab02178
diff --git a/telecomm/java/android/telecom/Phone.java b/telecomm/java/android/telecom/Phone.java
index ebd04c7..db2abf3 100644
--- a/telecomm/java/android/telecom/Phone.java
+++ b/telecomm/java/android/telecom/Phone.java
@@ -208,6 +208,13 @@
         }
     }
 
+    final void internalOnRttInitiationFailure(String callId, int reason) {
+        Call call = mCallByTelecomCallId.get(callId);
+        if (call != null) {
+            call.internalOnRttInitiationFailure(reason);
+        }
+    }
+
     /**
      * Called to destroy the phone and cleanup any lingering calls.
      */