Update use of init_data_types in encrypted media layout tests.

This changes all hardcoded values from content types to registered
init data types. Values from events are still passed as content types.

BUG=385874

Review URL: https://codereview.chromium.org/496543004

git-svn-id: svn://svn.chromium.org/blink/trunk@180742 bbb929c8-8fbe-4397-9dbb-9b2b20218538