Provide delivery URLs for attachments in PlaybackInfo.

MediaBrowser.Api/Playback/MediaInfoService.cs

@@ -524,6 +524,14 @@ namespace MediaBrowser.Api.Playback
                     SetDeviceSpecificSubtitleInfo(streamInfo, mediaSource, auth.Token);
                 }
             }
+
+            foreach (var attachment in mediaSource.MediaAttachments)
+            {
+                attachment.DeliveryUrl = string.Format("/Videos/{0}/{1}/Attachments/{2}/Attachment",
+                    item.Id,
+                    mediaSource.Id,
+                    attachment.Index);
+            }
         }
 
         private long? GetMaxBitrate(long? clientMaxBitrate, User user)

MediaBrowser.Model/Entities/MediaAttachment.cs

@@ -40,5 +40,11 @@ namespace MediaBrowser.Model.Entities
         /// </summary>
         /// <value>The MIME type.</value>
         public string MIMEType { get; set; }
+
+        /// <summary>
+        /// Gets or sets the delivery URL.
+        /// </summary>
+        /// <value>The delivery URL.</value>
+        public string DeliveryUrl { get; set; }
     }
 }