[chrome.displaySource] further implementation of call completion callbacks

extensions/common/api/display_source.idl

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // The <code>chrome.displaySource</code> API creates a Display
 // session using WebMediaStreamTrack as sources.
 namespace displaySource {
   enum ErrorType {
-    // A new Display session cannot be started before the existing one is
-    // terminated.
-    session_limit_error,
-
     // The connection with sink cannot be established or has dropped
     // unexpectedly.
     connection_error,
 
     // The capabilities of this Display Source and the connected  
     // sink do not fit (e.g. the sink cannot play the media content of
     // the formats given by the source).
     capabilities_negotiation_error,
 
     // There was an error in media pipeline: while encoding, packetizing or
@@ skipping 115 matching lines @@
     // Event fired when the Display session is terminated.
     // |sinkId| Id of the peer sink
     [nocompile] static void onSessionTerminated(long sinkId);
     // Event fired when an error occurs.
     // |sinkId| Id of the peer sink
     // |errorInfo| error description
     [nocompile] static void onSessionErrorOccured(long sinkId,
                                                   ErrorInfo errorInfo);
   };
 };