vaapi_jpeg_decoder{_unittest}: address some presubmit warnings

- s/arraysize/base::size/ (see crbug.com/837308#c15 for decltype trick).
- s/base::bind/base::BindRepeating/ (and s/Closure/RepeatingClosure/).

Bug: 876810, 837308
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I0068d55985c5c4fdcf1ed987e278f402fd0e6ac0
Reviewed-on: https://chromium-review.googlesource.com/1189103
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586137}
2 files changed