[Media Router] Add Connecting state to PresentationConnection to bring align with spec

content/common/presentation/presentation_service.mojom

 // 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.
 
 module presentation;
 
 struct PresentationSessionInfo {
   string url;
   string id;
 };
 
 enum PresentationConnectionState {
+  CONNECTING,
   CONNECTED,
   CLOSED,
   TERMINATED
 };
 
 enum PresentationErrorType {
   NO_AVAILABLE_SCREENS,
   SESSION_REQUEST_CANCELLED,
   NO_PRESENTATION_FOUND,
   UNKNOWN,
@@ skipping 95 matching lines @@
   OnConnectionStateChanged(PresentationSessionInfo connection,
                            PresentationConnectionState newState);
 
   // See PresentationService::ListenForSessionMessages.
   OnSessionMessagesReceived(PresentationSessionInfo sessionInfo,
                             array<SessionMessage> messages);
 
   // See PresentationService::SetDefaultPresentationURL.
   OnDefaultSessionStarted(PresentationSessionInfo sessionInfo);
 };