Request is not finished when using SqlDataReader in FileStreamResult using ASP.NET MVC

For performance considerations I am using SqlConnection and SqlReaderStream for returning a byte[] stream from a SQL Server database:

private static SqlConnection GetConnection()
{
    var sqlConnectionStringBuilder =
        new SqlConnectionStringBuilder(
            ConfigurationManager.ConnectionStrings["StudentsSystemEntities"].ConnectionString)
            {
                Pooling = true
            };
    var connection = new SqlConnection(sqlConnectionStringBuilder.ConnectionString);
    connection.Open();
    return connection;
}

public FileDownloadModel GetFileById(Guid fileId)
{
    var connection = GetConnection();
    var command = new SqlCommand(
        @"SELECT [FileSize], [FileExtension], [Content] FROM [dbo].[Files] WHERE [FileId] = @fileId;",
        connection);
    var paramFilename = new SqlParameter(@"fileId", SqlDbType.UniqueIdentifier) { Value = fileId };
    command.Parameters.Add(paramFilename);

    var reader = command.ExecuteReader(
        CommandBehavior.SequentialAccess | CommandBehavior.SingleResult
        | CommandBehavior.SingleRow | CommandBehavior.CloseConnection);

    if (reader.Read() == false) return null;

    var file = new FileDownloadModel
                    {
                        FileSize = reader.GetInt32(0),
                        FileExtension = reader.GetString(1),
                        Content = new SqlReaderStream(reader, 2)
                    };
    return file;
}

I am using this GetFileById method in ASP.NET MVC action:

[HttpGet]
public ActionResult Get(string id)
{
    // Validations omitted

    var file = this.filesRepository.GetFileById(guid);

    this.Response.Cache.SetCacheability(HttpCacheability.Public);
    this.Response.Cache.SetMaxAge(TimeSpan.FromDays(365));
    this.Response.Cache.SetSlidingExpiration(true);

    this.Response.AddHeader("Content-Length", file.FileSize.ToString());
    var contentType = MimeMapping.GetMimeMapping(
        string.Format("file.{0}", file.FileExtension));
    // this.Response.BufferOutput = false;
    return new FileStreamResult(file.Content, contentType);
}

I am connecting the MVC FileStreamResult with the SqlReaderStream in the following line:

return new FileStreamResult(file.Content, contentType);

When I try to load the resource using Chrome (or Firefox...) the entire file is loaded but I am getting the following error:

CAUTION: request is not finished yet!

Response headers:

HTTP/1.1 200 OK
Cache-Control: public, max-age=31536000
Content-Length: 33429
Content-Type: image/png
Server: Microsoft-IIS/10.0
X-AspNetMvc-Version: 5.2
X-AspNet-Version: 4.0.30319
X-SourceFiles: =?UTF-8?B?QzpcR---trimmed---G5n?=
X-Powered-By: ASP.NET
Date: Tue, 28 Jul 2015 13:02:55 GMT

Additional information:

• I am not using any Chrome extensions
• The problem is only with the given Get action. All other actions are loading normally
• The FilesController (in which the Get action is) inherits directly from the Controller class
• The file is loading successfully but the browser is still waiting the server:
• The exact same problem I am having with Firefox

What are the possible causes of the problem?

Source code of the SqlReaderStream class

public class SqlReaderStream : Stream
{
    private readonly int columnIndex;

    private SqlDataReader reader;

    private long position;

    public SqlReaderStream(
        SqlDataReader reader, 
        int columnIndex)
    {
        this.reader = reader;
        this.columnIndex = columnIndex;
    }

    public override long Position
    {
        get { return this.position; }
        set { throw new NotImplementedException(); }
    }

    public override bool CanRead
    {
        get { return true; }
    }

    public override bool CanSeek
    {
        get { return false; }
    }

    public override bool CanWrite
    {
        get { return false; }
    }

    public override long Length
    {
        get { throw new NotImplementedException(); }
    }

    public override void Flush()
    {
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        var bytesRead = this.reader.GetBytes(
            this.columnIndex, this.position, buffer, offset, count);
        this.position += bytesRead;
        return (int)bytesRead;
    }

    public override long Seek(long offset, SeekOrigin origin)
    {
        throw new NotImplementedException();
    }

    public override void SetLength(long value)
    {
        throw new NotImplementedException();
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        throw new NotImplementedException();
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing && null != this.reader)
        {
            this.reader.Dispose();
            this.reader = null;
        }

        base.Dispose(disposing);
    }
}