message: Track decryption success/failure rate with piwik
  Emit a piwik event when a decryption occurs in the category "E2E" with
  the action "Decryption result" and the name either "failure" or
  "success".
  NB: This will cause Riot to a lot of networking when decrypting many
  events. One HTTP request per decrypted event should be expected.
diff: @@ -1308,6 +1308,15 @@ export default React.createClass({
  }
  });
  + // XXX: This will do a HTTP request for each Event.decrypted event
  + cli.on("Event.decrypted", (e) => {
  + if (e.isDecryptionFailure()) {
  + Analytics.trackEvent('E2E', 'Decryption result', 'failure');
  + } else {
  + Analytics.trackEvent('E2E', 'Decryption result', 'success');
  + }
  + });
  +
  const krh = new KeyRequestHandler(cli);
  cli.on("crypto.roomKeyRequest", (req) => {
  krh.handleKeyRequest(req);
  