Hide charge-inducing features. Intercept link interstitials sooner.

* HTTPS can cause charges. This hides obvious HTTPS chrome until safe.
* Rewritten hyperlinks normally result in a server roundtrip upon click.
* This patch tries to render a client-side interstitial opportunistically.
* However, without binding to all click events, some clicks will default to the server.
* For hyperlinks that look like Wikipedia language switches, a last-ditch server check is allowed.
* Eventually, HTTPS will be supported via IP zero-rating. At that point, this code should be updated.

Change-Id: Icd8c9140e3a22de60e148670f7bbc67a356950d8
Merge "Hide charge-inducing features. Intercept link interstitials sooner."