net/http: FileServer calls FileSystem.Open with unclean path for //index.html

[bradfitz]

The FileServer Handler can call FileSystem.Open with an unclean path of
"//index.html" or similar.

(As reported on golang-dev.)

[gopherbot]

Comment 1:

CL https://golang.org/cl/142090043 mentions this issue.

[bradfitz]

Comment 2:

This issue was closed by revision bb43124.

Status changed to Fixed.