DevTools: Make sure all variations of "*gray" are also recognized as "*grey"

R=pfeldman, sergeyv
BUG=377491
NOTRY=true

Review URL: https://codereview.chromium.org/304513003

git-svn-id: svn://svn.chromium.org/blink/trunk@174849 bbb929c8-8fbe-4397-9dbb-9b2b20218538