"Download as CSV" results in .css file on disk

# Current behavior

When clicking the "Download as CSV" link, the download (via Chrome) actual results in a file named ".css" (sic!).
When trying to open it, an application for a Cascading Style Sheets is suggested.
The content of the file actually is in CSV format, which is good.

Interesting response headers from the download request:
* content-disposition: "attachment; filename=interactive-landscape.csv" (correct, but extension is not used by Chrome!)
* content-type: "text/css" (not correct!)

The browser ignores the supplied file name extension and renames it to ".css".

# Expected behavior

Response carries content type header with value "text/csv".
File actually downloads with a CSV extension, is easily opened by a CSV-handling application.

Looks like a one character fix.