This warning was found by the GN build on Windows: the FAIL macro contains
a return which caused code after the FAIL to be unreachable.

BUG=angleproject:929

Change-Id: Id4bda39ea9f76d2b59c44391cb2de8a3bfb6947c
Reviewed-on: https://chromium-review.googlesource.com/296950Tested-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>