This build is mainly to work around a serious bug in iOS 9 that prevents any audio playback. The linked post contains more information, but this build includes a workaround. Previously the first audio playback (and any video playback) was delayed until the next touch start event, since playback could only begin in a user input event. iOS 9 has a bug that means playback cannot begin even in the touch start event. The workaround is to delay it further to the touch end event, which also counts as a user input event but playback can still begin in iOS 9. This generally resolves the issue with little noticable change, but note there could be side effects if you have events that depend on playback starting earlier. This is all we can do until Apple fix the bug; follow WebKit bug 149367 for updates from Apple's side. Please note all previously published content is affected and will need to be republished with this release or newer to work around the iOS 9 bug!
This build also includes code to enable-by-default the new JIT-enabled WKWebView on iOS 9, but this relies on a Cordova update which is not out yet. We'll be following up with a blog post including more detail about this when it takes effect, but when it comes it should bring significantly improved performance for iOS apps published with Cordova.