Apps that target KITKAT or below default to allowing third party cookies. Apps targeting LOLLIPOP or later default to disallowing third party cookies.
Android 5.0 changes the default behavior for your app.
If your app targets API level 21 or higher:
The system blocks mixed content and third party cookies by default. To allow mixed content and third party cookies, use the setMixedContentMode() and setAcceptThirdPartyCookies() methods respectively.
The system now intelligently chooses portions of the HTML document to draw. This new default behavior helps to reduce memory footprint and increase performance. If you want to render the whole document at once, disable this optimization by calling enableSlowWholeDocumentDraw().
If your app targets API levels lower than 21: The system allows mixed content and third party cookies, and always renders the whole document at once.
Workaround in the "Comments" section...