Older browsers `document.visibilityState`

[Saartje87]

For example Android 4.4 doesn't supports document.visibilityState without the webkit prefix, creating an animation with a delay will never be triggered on these devices because isDocumentVisible will not return false.
Is it an idea to check for 'visibilityState' in document and then return the document visibility or true for older browsers?

[michaelvillar]

Yep can probably do that!