Disable WebP layout tests that need to be updated after sync to v0.4.0

BUG=331619
R=fbarchard@chromium.org

Review URL: https://codereview.chromium.org/122463005

git-svn-id: svn://svn.chromium.org/blink/trunk@164539 bbb929c8-8fbe-4397-9dbb-9b2b20218538