Rewrap comments to 80 columns in Source/platform/graphics/paint/.
This also makes some minor modifications (rewrite for clarity, etc.).
BUG=
563793
TEST=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Committed:
https://crrev.com/980f63ea8f6c7b647e6cdd7e773903fc536ec1a5
Cr-Commit-Position: refs/heads/master@{#423031}