Value of Content-Disposition header:
Content-Disposition: attachment; foo="\"\\";filename="foo.html"
Test Description:
'attachment', specifying a filename of foo.html
and an extension parameter "foo" which should be ignored
(see Section 4.4 of RFC 6266.).
In comparison to attwithfilenameandextparam,
the extension parameter actually uses backslash-escapes. This tests whether the
UA properly skips the parameter.
UA should offer to download the resource as "foo.html".