Handle windows test names correctly when linting SmokeTests.

(Speculating that this fixes the problem ... this is probably the wrong
fix and port.tests() should not be returning windows paths, but I'll
double-check that later after I un-break the build).

TBR=ojan@chromium.org
BUG=321863

Review URL: https://codereview.chromium.org/102723006

git-svn-id: svn://svn.chromium.org/blink/trunk@163835 bbb929c8-8fbe-4397-9dbb-9b2b20218538