ASP.NET Web API downloading text

I have a WebAPI controller that need to download some files depending of the request, but when it comes to plain text files it doesnt give me the browser's download requisition. It only give me the plain text response like it was JSON (in my case, it's a JSONP WebAPI).

I've checked others Q&A from stack (and other sites), but I still got nothing:

• Is there a way to force ASP.NET Web API to return plain text?

• Returning binary file from controller in ASP.NET Web API

• ASP .Net Web API downloading images as binary

Here it goes my current code:

var httpResponse = new HttpResponseMessage(HttpStatusCode.OK);
httpResponse.Content = new StreamContent(new MemoryStream(Encoding.UTF8.GetBytes(content)));
httpResponse.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
httpResponse.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
httpResponse.Content.Headers.ContentDisposition.FileName = "speedcam.txt";
return httpResponse;

And this is Chrome's response:

Cache-Control:no-cache

Content-Disposition:attachment; filename=speedcam.txt

Content-Length:17462

Content-Type:application/octet-stream

Date:Mon, 27 Aug 2012 04:53:23 GMT

Expires:-1

Pragma:no-cache

Server:Microsoft-IIS/8.0

X-AspNet-Version:4.0.30319

X-Powered-By:ASP.NET

X-SourceFiles:=?UTF-8?B?TTpcVHJhYmFsaG9cTWFwYVJhZGFyXE1hcGFSYWRhci5XZWJBUEk0XEV4cG9ydGE=?

Seems OK, but the whole file text is in the Chrome Dev Tools "Response Tab"..