FIX: Ensure topic route does not replaceState after navigation (#24563)

This hook is `cancel()`'d in a willTransition hook, but that isn't always enough. It might still be scheduled if there is a scroll event between `willTransition`, and the transition actually completing. Following c2d94be06e, this kind of scroll event happens when the loading indicator is set to 'spinner'. This would put the router in a weird state and cause navigation issues.

Also takes the opportunity to remove JQuery from this code path

https://meta.discourse.org/t/286463/15

app/assets/javascripts/discourse/app/routes/topic.js

@@ -2,7 +2,6 @@ import { action, get } from "@ember/object";
 import { cancel, schedule } from "@ember/runloop";
 import { inject as service } from "@ember/service";
 import { isEmpty } from "@ember/utils";
-import $ from "jquery";
 import AddPmParticipants from "discourse/components/modal/add-pm-participants";
 import ChangeOwnerModal from "discourse/components/modal/change-owner";
 import ChangeTimestampModal from "discourse/components/modal/change-timestamp";
@@ -29,6 +28,7 @@ const TopicRoute = DiscourseRoute.extend({
   composer: service(),
   screenTrack: service(),
   modal: service(),
+  router: service(),
 
   scheduledReplace: null,
   lastScrollPos: null,
@@ -244,8 +244,7 @@ const TopicRoute = DiscourseRoute.extend({
   // Use replaceState to update the URL once it changes
   @action
   postChangedRoute(currentPost) {
-    // do nothing if we are transitioning to another route
-    if (this.isTransitioning || TopicRoute.disableReplaceState) {
+    if (TopicRoute.disableReplaceState) {
       return;
     }
 
@@ -279,11 +278,12 @@ const TopicRoute = DiscourseRoute.extend({
       cancel(this.scheduledReplace);
 
       this.setProperties({
-        lastScrollPos: parseInt($(document).scrollTop(), 10),
+        lastScrollPos: document.scrollingElement.scrollTop,
         scheduledReplace: discourseLater(
           this,
           "_replaceUnlessScrolling",
           postUrl,
+          topic.id,
           SCROLL_DELAY
         ),
       });
@@ -299,18 +299,28 @@ const TopicRoute = DiscourseRoute.extend({
   },
 
   @action
-  willTransition(transition) {
+  willTransition() {
     this._super(...arguments);
     cancel(this.scheduledReplace);
-    this.set("isTransitioning", true);
-    transition.catch(() => this.set("isTransitioning", false));
     return true;
   },
 
   // replaceState can be very slow on Android Chrome. This function debounces replaceState
   // within a topic until scrolling stops
-  _replaceUnlessScrolling(url) {
-    const currentPos = parseInt($(document).scrollTop(), 10);
+  _replaceUnlessScrolling(url, topicId) {
+    const { currentRouteName } = this.router;
+
+    const stillOnTopicRoute = currentRouteName.split(".")[0] === "topic";
+    if (!stillOnTopicRoute) {
+      return;
+    }
+
+    const stillOnSameTopic = this.modelFor("topic").id === topicId;
+    if (!stillOnSameTopic) {
+      return;
+    }
+
+    const currentPos = document.scrollingElement.scrollTop;
     if (currentPos === this.lastScrollPos) {
       DiscourseURL.replaceState(url);
       return;
@@ -322,6 +332,7 @@ const TopicRoute = DiscourseRoute.extend({
         this,
         "_replaceUnlessScrolling",
         url,
+        topicId,
         SCROLL_DELAY
       ),
     });
@@ -368,11 +379,6 @@ const TopicRoute = DiscourseRoute.extend({
     }
   },
 
-  activate() {
-    this._super(...arguments);
-    this.set("isTransitioning", false);
-  },
-
   deactivate() {
     this._super(...arguments);
 
@@ -393,9 +399,6 @@ const TopicRoute = DiscourseRoute.extend({
   },
 
   setupController(controller, model) {
-    // In case we navigate from one topic directly to another
-    this.set("isTransitioning", false);
-
     controller.setProperties({
       model,
       editingTopic: false,