Previously the index variable was missing a precision. This may have
been behind loop-based init failing on some Android platforms.

BUG=chromium:735497
TEST=angle_unittests

Change-Id: I0307891dfb2edf6c52efd5b495f602b380263d65
Reviewed-on: https://chromium-review.googlesource.com/822413Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>