Add edge case for iPhone standalone in scheduler which does not fire …

src/schedule.js

@@ -4,29 +4,47 @@ var util = require("./util");
 var noAsyncScheduler = function() {
     throw new Error(NO_ASYNC_SCHEDULER);
 };
+// This file figures out which scheduler to use for Bluebird. It normalizes
+// async task scheduling across target platforms. Note that not all JS target 
+// platforms come supported. The scheduler is overridable with `setScheduler`
+
+// Our scheduler for NodeJS/io.js is setImmediate for recent 
+// versions of node because of macrotask semantics. 
+// The `typeof` check is for an edge case with nw.js 
 if (util.isNode && typeof MutationObserver === "undefined") {
     var GlobalSetImmediate = global.setImmediate;
     var ProcessNextTick = process.nextTick;
     schedule = util.isRecentNode
                 ? function(fn) { GlobalSetImmediate.call(global, fn); }
                 : function(fn) { ProcessNextTick.call(process, fn); };
-} else if (typeof MutationObserver !== "undefined") {
+// Outside of Node, we're using MutationObservers because they provide low
+// latency. The second check is to guard against iOS standalone apps which
+// do not fire DOM mutation events for some reason on iOS 8.3+
+} else if ((typeof MutationObserver !== "undefined") && 
+          !(typeof window !== "undefined" && 
+            window.navigator && 
+            window.navigator.standalone)) {
     schedule = function(fn) {
         var div = document.createElement("div");
         var observer = new MutationObserver(fn);
         observer.observe(div, {attributes: true});
         return function() { div.classList.toggle("foo"); };
     };
     schedule.isStatic = true;
+// setImmediate has higher latency but is still pretty good. This is useful for
+// cases where MutationObserver is not defined (older IE, for example)
 } else if (typeof setImmediate !== "undefined") {
     schedule = function (fn) {
         setImmediate(fn);
     };
+// setTimeout also works, it has the most latency but it does the trick. 
 } else if (typeof setTimeout !== "undefined") {
     schedule = function (fn) {
         setTimeout(fn, 0);
     };
 } else {
+// Do __Not__ default to a sync scheduler, that would break Promises/A+ 
+// compliancy and cause race conditions.
     schedule = noAsyncScheduler;
 }
 module.exports = schedule;