Add touch-action:manipulation to future-proof avoidance of 300ms click delay?

Created by: cvrebert

In particular, the next iOS Safari feature release should (modulo secret Apple machinations) support it (see http://trac.webkit.org/changeset/191452), whereas it's uncertain whether WebKit will (ever) decide to remove the delay on all pages with mobile viewports (see https://bugs.webkit.org/show_bug.cgi?id=150469) like Chrome et al. already do. Some background on the delay: http://developer.telerik.com/featured/300-ms-click-delay-ios-8/ CC: Touchy guy @patrickhlauke