Fix not disposing callback in ResourceHandler.Skip (#3978)

Author: chylex

CefSharp.Example/AcceptRangeResourceHandler.cs

@@ -151,6 +151,9 @@ private bool TryGetRangeHeader(out string contentRange, out int contentLength)
 
         bool IResourceHandler.Skip(long bytesToSkip, out long bytesSkipped, IResourceSkipCallback callback)
         {
+            //We don't need the callback, as it's an unmanaged resource we should dispose it (could wrap it in a using statement).
+            callback.Dispose();
+
             //No Stream or Stream cannot seek then we indicate failure
             if (stream == null || !stream.CanSeek)
             {

CefSharp/ResourceHandler.cs

@@ -138,6 +138,9 @@ bool IResourceHandler.Open(IRequest request, out bool handleRequest, ICallback c
 
         bool IResourceHandler.Skip(long bytesToSkip, out long bytesSkipped, IResourceSkipCallback callback)
         {
+            //We don't need the callback, as it's an unmanaged resource we should dispose it (could wrap it in a using statement).
+            callback.Dispose();
+
             //No Stream or Stream cannot seek then we indicate failure
             if (Stream == null || !Stream.CanSeek)
             {