FIX: Don't process infinite scrolling while safari hacks are active

app/assets/javascripts/discourse/components/scrolling-post-stream.js.es6

@@ -2,6 +2,7 @@ import DiscourseURL from 'discourse/lib/url';
 import { keyDirty } from 'discourse/widgets/widget';
 import MountWidget from 'discourse/components/mount-widget';
 import { cloak, uncloak } from 'discourse/widgets/post-stream';
+import { isWorkaroundActive } from 'discourse/lib/safari-hacks';
 
 function findTopView($posts, viewportTop, min, max) {
   if (max < min) { return min; }
@@ -38,6 +39,7 @@ export default MountWidget.extend({
 
   scrolled() {
     if (this.isDestroyed || this.isDestroying) { return; }
+    if (isWorkaroundActive()) { return; }
 
     const $w = $(window);
     const windowHeight = window.innerHeight ? window.innerHeight : $w.height();

app/assets/javascripts/discourse/lib/safari-hacks.js.es6

@@ -6,6 +6,11 @@ function applicable() {
          !navigator.userAgent.match(/Trident/g);
 }
 
+let workaroundActive = false;
+export function isWorkaroundActive() {
+  return workaroundActive;
+}
+
 // per http://stackoverflow.com/questions/29001977/safari-in-ios8-is-scrolling-screen-when-fixed-elements-get-focus/29064810
 function positioningWorkaround($fixedElement) {
   if (!applicable()) {
@@ -37,12 +42,12 @@ function positioningWorkaround($fixedElement) {
     if (evt) {
       evt.target.removeEventListener('blur', blurred);
     }
+    workaroundActive = false;
   };
 
   var blurred = _.debounce(blurredNow, 250);
 
   var positioningHack = function(evt){
-
     const self = this;
     done = false;
 
@@ -76,6 +81,7 @@ function positioningWorkaround($fixedElement) {
 
     evt.preventDefault();
     self.focus();
+    workaroundActive = true;
   };
 
   function attachTouchStart(elem, fn) {