Adding method to get disconnect cause from conference

Bug: 17842499
Change-Id: Ifb6e61d50d66aa8e8299e7024b2ab6d1d0f9d878

api/current.txt

@@ -28101,6 +28101,7 @@ package android.telecom {
     method public final int getCapabilities();
     method public final java.util.List<android.telecom.Connection> getConferenceableConnections();
     method public final java.util.List<android.telecom.Connection> getConnections();
+    method public final android.telecom.DisconnectCause getDisconnectCause();
     method public final android.telecom.PhoneAccountHandle getPhoneAccountHandle();
     method public android.telecom.Connection getPrimaryConnection();
     method public final int getState();

telecomm/java/android/telecom/Conference.java

@@ -206,6 +206,13 @@ public abstract class Conference {
         }
     }
 
+    /**
+     * @return The {@link DisconnectCause} for this connection.
+     */
+    public final DisconnectCause getDisconnectCause() {
+        return mDisconnectCause;
+    }
+
     /**
      * Sets the capabilities of a conference. See {@link PhoneCapabilities} for valid values.
      *