Fix to display merge icon on failure.

Trigger a state change to incallui with the existing state
on an unsuccessful merge in order to enable merge icon.

Change-Id: I6bb3a151f27e38cf788cb148ce61005b62cb8e2b
CRs-Fixed: 815642
diff --git a/src/com/android/server/telecom/CallsManager.java b/src/com/android/server/telecom/CallsManager.java
index 8c6e4cf..8d164ec 100644
--- a/src/com/android/server/telecom/CallsManager.java
+++ b/src/com/android/server/telecom/CallsManager.java
@@ -82,6 +82,7 @@
         void onVideoStateChanged(Call call);
         void onCanAddCallChanged(boolean canAddCall);
         void onSessionModifyRequestReceived(Call call, VideoProfile videoProfile);
+        void onMergeFailed(Call call);
     }
 
     private static final String TAG = "CallsManager";
@@ -2296,4 +2297,12 @@
             updateForegroundCall();
         }
     }
+
+    void onMergeFailed(Call call) {
+        if (mCalls.contains(call)) {
+            for (CallsManagerListener listener : mListeners) {
+                listener.onMergeFailed(call);
+            }
+        }
+    }
 }