Round GPU tiles to multiple of 64 to work around CA scaling issues

When scaling tiles using Core Animation, certain tile sizes / scale
factors appear to cause rounding issues and seams between tiles.

Rounding tiles to a multiple of 64 works around the
most obvious case of this, which is seen on the print preview screen.

BUG=632274
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel;master.tryserver.blink:win10_blink_rel;master.tryserver.blink:mac10.11_blink_rel

Committed: https://crrev.com/dfe9acda5549bd8c3442c411ffc4f8c76c0977f3
Review-Url: https://codereview.chromium.org/2251583002
Cr-Original-Commit-Position: refs/heads/master@{#412698}
Cr-Commit-Position: refs/heads/master@{#412917}
3 files changed