[CSS Grid Layout] Update WATCHLIST after move to layout/LayoutGrid
[CSS Grid Layout] Update WATCHLIST after move to layout/LayoutGrid

After the rename in r190772, change "rendering/" path by "layout/" in
the grid layout WATCHLIST. Include "paint/" in the list too.

BUG=450612

Review URL: https://codereview.chromium.org/964473002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@190924 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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