Revert of [test] Fix cctest path separators on Windows

Revert of [test] Fix cctest path separators on Windows (patchset #2 id:20001 of https://codereview.chromium.org/1348653003/ )

Reason for revert:
mozilla tests are failing on Windows

Original issue's description:
> [test] Fix cctest path separators on Windows
>
> Now run-tests.py understands "suite/foo/bar" with forward slashes for
> command-line test selection on all test suites on all platforms.
>
> Previously, file-based suites like mjsunit also accepted "mjsunit/foo\bar";
> that behavior is sacrificed here in favor of unification. For the cctest
> suite, OTOH, it wasn't possible on Windows to select specific tests at all.
>
> Committed: https://crrev.com/b36cfdb39ae648b49a1396c4f669df9b1f57996c
> Cr-Commit-Position: refs/heads/master@{#30794}

TBR=machenbach@google.com,machenbach@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/5f44a9105980e7ca3a444c9c4293ee9442a8139f
Cr-Commit-Position: refs/heads/master@{#30795}

[Jakob Kummerow, 2015-09-17 11:59:54]

Created Revert of [test] Fix cctest path separators on Windows

[commit-bot: I haz the power, 2015-09-17 12:00:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1349163002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1349163002/1

[commit-bot: I haz the power, 2015-09-17 12:00:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-17 12:00:33]

Patchset 1 (id:??) landed as
https://crrev.com/5f44a9105980e7ca3a444c9c4293ee9442a8139f
Cr-Commit-Position: refs/heads/master@{#30795}

[Jakob Kummerow, 2015-09-17 12:44:56]

Reland: https://codereview.chromium.org/1356613002