The JSON data stream that feeds Piwik's Open Flash Chart widgets (e.g., when the URL contains the viewDataTable param) is sent with the text/html header. This should be set to application/json to prevent content munging by "bad" hosts.
Abandoned, in favor of comment:ticket:997:1
In ,fixes #994 - set content-type to application/json for OFC data feed. Needed for embedded objects.