fixes #746 - Problems with playstate for multiple local trailers for the same movie

MediaBrowser.Controller/Entities/Trailer.cs

@@ -3,8 +3,9 @@ using MediaBrowser.Model.Configuration;
 using MediaBrowser.Model.Entities;
 using System;
 using System.Collections.Generic;
-using System.Runtime.Serialization;
+using System.Globalization;
 using System.Linq;
+using System.Runtime.Serialization;
 
 namespace MediaBrowser.Controller.Entities
 {
@@ -92,6 +93,12 @@ namespace MediaBrowser.Controller.Entities
             {
                 key = key + "-trailer";
 
+                // Make sure different trailers have their own data.
+                if (RunTimeTicks.HasValue)
+                {
+                    key += "-" + RunTimeTicks.Value.ToString(CultureInfo.InvariantCulture);
+                }
+
                 return key;
             }