Re-enable EME Layout Tests now that Clear Key is available again.

Also update the syntax test due to changes in r157966.

BUG=291290

Review URL: https://chromiumcodereview.appspot.com/24253002

git-svn-id: svn://svn.chromium.org/blink/trunk@158039 bbb929c8-8fbe-4397-9dbb-9b2b20218538