[LayoutNG] Add layout_ng try bots for core/paint/ng and FlagExpectations

This patch adds layout_ng try bots for following directories:
- Source/core/paint/ng
- LayoutTests/FlagExpectations/enable-blink-features=LayoutNG
- LayoutTests/flag-specific/enable-blink-features=LayoutNG
in the same way as slimming-paint does.

Bug: 591099, 708452
Change-Id: I1d4f5d0655794837f6292f0030862cece6db4f55
Reviewed-on: https://chromium-review.googlesource.com/822553
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523604}
1 file changed