Motivation:
Currently the way a 'null' origin, a request that most often indicated
that the request is coming from a file on the local file system, is
handled is incorrect. We are currently returning a wildcard origin '*'
but should be returning 'null' for the 'Access-Control-Allow-Origin'
which is valid according to the specification [1].
Modifications:
Updated CorsHandler to add a 'null' origin instead of the '*' origin in
the case the request origin is 'null.
Result:
All test pass and the CORS example as does the cors.html example if you
try to serve it by opening the file directly in a web browser.
[1]
https://www.w3.org/TR/cors/#access-control-allow-origin-response-header