FIX: dfp category targeting params

DFP category targeting param wasn't always being updated on topic
list pages.

Also remove dependency on a category param being passed in to the
component from a template so that we can now place dfp ads
in places that don't have access to the current category and
targeting will still work.

assets/javascripts/discourse/components/ad-component.js.es6

@@ -8,6 +8,11 @@ export default Ember.Component.extend({
     "router.currentRoute.parent.attributes.category_id"
   ),
 
+  currentCategorySlug: Ember.computed.or(
+    "router.currentRoute.attributes.category.slug",
+    "router.currentRoute.parent.attributes.category.slug"
+  ),
+
   @computed("currentUser.groups")
   showToGroups(groups) {
     const currentUser = Discourse.User.current();

assets/javascripts/discourse/components/google-dfp-ad.js.es6

@@ -266,22 +266,23 @@ export default AdComponent.extend({
     return this.isNthPost(parseInt(this.siteSettings.dfp_nth_post_code));
   },
 
-  @observes("refreshOnChange")
+  @on("didUpdate")
-  refreshAd() {
+  updated() {
-    var slot = ads[this.get("divId")];
+    if (this.get("listLoading")) {
+      return;
+    }
+
+    let slot = ads[this.get("divId")];
     if (!(slot && slot.ad)) {
       return;
     }
 
-    var self = this,
+    let ad = slot.ad,
-      ad = slot.ad;
+      categorySlug = this.get("currentCategorySlug");
 
-    if (this.get("loadedGoogletag") && this.get("refreshOnChange")) {
+    if (this.get("loadedGoogletag")) {
       window.googletag.cmd.push(function() {
-        ad.setTargeting(
+        ad.setTargeting("discourse-category", categorySlug || "0");
-          "discourse-category",
-          self.get("category") ? self.get("category") : "0"
-        );
         window.googletag.pubads().refresh([ad]);
       });
     }
@@ -293,7 +294,7 @@ export default AdComponent.extend({
       return;
     }
 
-    var self = this;
+    let self = this;
     loadGoogle(this.siteSettings).then(function() {
       self.set("loadedGoogletag", true);
       window.googletag.cmd.push(function() {
@@ -306,7 +307,7 @@ export default AdComponent.extend({
         if (slot && slot.ad) {
           slot.ad.setTargeting(
             "discourse-category",
-            self.get("category") ? self.get("category") : "0"
+            self.get("currentCategorySlug") || "0"
           );
           window.googletag.display(self.get("divId"));
           window.googletag.pubads().refresh([slot.ad]);