app: fix shiny build.

Fixes golang/go#14401.

Change-Id: Id8bbc69e8dcb397094c165e97946d4d2688f34ad
Reviewed-on: https://go-review.googlesource.com/19872
Reviewed-by: David Crawshaw <crawshaw@golang.org>

app/shiny.go

@@ -39,8 +39,8 @@ func main(f func(a App)) {
 
 		go f(theApp)
 
-		for e := range w.Events() {
-			theApp.Send(convertEvent(e))
+		for {
+			theApp.Send(convertEvent(w.NextEvent()))
 		}
 	})
 }