PrintMarker was printing 50 NUL bytes before the marker.
Also, the examples for writing your own ShouldEnable helper suggest
"if m == nil { return false }", but this is inconsistent with how
Matcher.ShouldEnable handles nil pointers.
Change-Id: Ie45075ba7fb8fcc63eadce9d793a06ef0c8aa9f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/517615
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>