Fix incorrect PathParameter overload being called. BUG=angleproject:1382 Change-Id: I9fd6e20b9487f9d7817865bc9129a60fc833d0ca Reviewed-on: https://chromium-review.googlesource.com/354030 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>