Fix webkit user script messages not being called when web view is hidden (#93)

* Call postMessage immediately when document is not visible

* Use document.hidden instead of comparing visibilityState

visibilityState may be options other than “hidden” that are considered
hidden, like prerender.

Author: zachwaugh

Turbolinks/WebView.js

@@ -97,10 +97,15 @@
         },
 
         postMessageAfterNextRepaint: function(name, data) {
-            var postMessage = this.postMessage.bind(this, name, data)
-            requestAnimationFrame(function() {
-                requestAnimationFrame(postMessage)
-            })
+            // Post immediately if document is hidden or message may be queued by call to rAF
+            if (document.hidden) {
+                this.postMessage(name, data);
+            } else {
+                var postMessage = this.postMessage.bind(this, name, data)
+                requestAnimationFrame(function() {
+                    requestAnimationFrame(postMessage)
+                })
+            }
         }
     }