refactor/rename: attempt to fix windows test, 2nd attempt.
refactor/rename: attempt to fix windows test, 2nd attempt.

Windows doesn't regard "/go/src" as an absolute path,
so we must explicitly define the virtual IsAbsPath method.

LGTM=gri
R=gri, sameer
CC=golang-codereviews
https://codereview.appspot.com/147100043

karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools