These backwards slashes happen with some versions of gyp.

Change-Id: I6c61e212aa34999fb82d74d9f1605d674f34fce0
Reviewed-on: https://chromium-review.googlesource.com/178522Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Commit-Queue: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>