Disable some WebP layout tests in virtual suite too.

This is a follow-up of http://crrev.com/122463005

Test expectations for virtual suites aren't derived from the non-virtual
ones. So need to explicitly disable these too.

TBR=fbarchard

BUG=331619

Review URL: https://codereview.chromium.org/129923004

git-svn-id: svn://svn.chromium.org/blink/trunk@164725 bbb929c8-8fbe-4397-9dbb-9b2b20218538