Remove the --enable-slimming-paint-v2 command-line switch

This patch removes --enable-slimming-paint-v2 as it has been
replaced by --enable-blink-features=CompositeAfterPaint

Bug: 909899
Change-Id: Iaed77958dfb01337aa0773f3ee064434357fa525
Reviewed-on: https://chromium-review.googlesource.com/c/1363830
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614113}
5 files changed