Cookie updated whenever ageRestrictedContent setting is changed or
service is changed. Right now there is only a cookie for youtube, but
cookies for other services could be added in the future.
Problems with this approach: Even when the service is set to youtube,
the downloader doesn't only request youtube urls e.g. it also sends
reqeusts to i.ytimg.com, suggestqueries.google.com, and yt3.ggpht.com.
The ageRestrictedContent cookie is not normally sent when sending
requests to these other urls, so doing so might have unknown effects.
Try to get cookies from pages even when they start loading, because non-html pages like ones with `pbj=1` never stop loading.
Try to extract the cookie directly from the redirection url, by looking at the field "google_abuse=".
Add `GOOGLE_ABUSE_EXEMPTION=` to the youtube recaptcha cookies.
Sometimes YouTube introduces recaptchas only on some pages. By loading the url inside the ReCaptchaException into ReCaptchaActivity's webview, the page that originally caused the problem is shown. The user can then solve the page-specific recaptcha.
* Activities will start reCaptchaActivity with startActivityForResult and
look for RECAPTCHA_REQUEST and RESULT_OK | RESULT_CANCELED in : 'onActivityResult()'
* ReCaptchas are implemented using a simple WebView with Javascript enable.
* All HTTP responses inside the WebView are catched (using onPageFinished())
** When Google reCatcha cookies are detected, register cookies to the
Downloader class and Return to MainActivity
