Skip these encrypted-media rather than trying to use fine-grained suppressions.

R=ddorwin@chromium.org
TBR=ddorwin

Review URL: https://codereview.chromium.org/23600052

git-svn-id: svn://svn.chromium.org/blink/trunk@157802 bbb929c8-8fbe-4397-9dbb-9b2b20218538