The JPEGDecoder ceils when rounding floats for mip level sizes while the
cc code floors. This results in 1 pixel differences in the scaled sizes
when using decode to scale. Avoid this by switching the cc mip size
calculations to match the decoder.

R=ericrk@chromium.org, chrishtr@chromium.org

Bug: 761565,558070
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I07069a4eff582ffbb621388ccae32b18aedebd3a
Reviewed-on: https://chromium-review.googlesource.com/1107049
Commit-Queue: Khushal <khushalsagar@chromium.org>
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Eric Karl <ericrk@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569626}