On Windows, file URLs should look like file:///C:/foo/bar instead of
file://C:/foo/bar. In the latter case, the "C:" is parsed as the host.
Updates golang/go#31675
Change-Id: I7f75be44dd5d289de3ffdbd20a78130ed03cd233
Reviewed-on: https://go-review.googlesource.com/c/tools/+/173918
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Ian Cottrell <iancottrell@google.com>