Because gtest's FAIL macro does a return, MSVC complained that the
update part of a range-based for loop was unreachable. Fixed this by
having a boolean value set to true if we execute the loop body.

BUG=angleproject:929

Change-Id: I6c1fec7ed6cf1a3aba6f02b68c1015bee2feebfd
Reviewed-on: https://chromium-review.googlesource.com/296730Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>