chore(Ads): Simplify quartile management in Interstitials (#7689)

Author: avelad

lib/ads/interstitial_ad_manager.js

@@ -704,7 +704,6 @@ shaka.ads.InterstitialAdManager = class {
       this.onEvent_(new shaka.util.FakeEvent(
           shaka.ads.Utils.AD_SKIP_STATE_CHANGED));
     }
-    const eventsSent = new Set();
     this.adEventManager_.listenOnce(this.player_, 'error', error);
     this.adEventManager_.listen(this.video_, 'timeupdate', () => {
       const duration = this.video_.duration;
@@ -718,23 +717,21 @@ shaka.ads.InterstitialAdManager = class {
             new shaka.util.FakeEvent(shaka.ads.Utils.AD_SKIP_STATE_CHANGED));
       }
       prevCanSkipNow = currentCanSkipNow;
-      const currentPercent = 100 * this.video_.currentTime / duration;
-      if (currentPercent >= 25 && !eventsSent.has('firstquartile')) {
-        updateBaseVideoTime();
-        this.onEvent_(
-            new shaka.util.FakeEvent(shaka.ads.Utils.AD_FIRST_QUARTILE));
-        eventsSent.add('firstquartile');
-      } else if (currentPercent >= 50 && !eventsSent.has('midpoint')) {
-        updateBaseVideoTime();
-        this.onEvent_(
-            new shaka.util.FakeEvent(shaka.ads.Utils.AD_MIDPOINT));
-        eventsSent.add('midpoint');
-      } else if (currentPercent >= 75 && !eventsSent.has('thirdquartile')) {
-        updateBaseVideoTime();
-        this.onEvent_(
-            new shaka.util.FakeEvent(shaka.ads.Utils.AD_THIRD_QUARTILE));
-        eventsSent.add('thirdquartile');
-      }
+    });
+    this.adEventManager_.listenOnce(this.player_, 'firstquartile', () => {
+      updateBaseVideoTime();
+      this.onEvent_(
+          new shaka.util.FakeEvent(shaka.ads.Utils.AD_FIRST_QUARTILE));
+    });
+    this.adEventManager_.listenOnce(this.player_, 'midpoint', () => {
+      updateBaseVideoTime();
+      this.onEvent_(
+          new shaka.util.FakeEvent(shaka.ads.Utils.AD_MIDPOINT));
+    });
+    this.adEventManager_.listenOnce(this.player_, 'thirdquartile', () => {
+      updateBaseVideoTime();
+      this.onEvent_(
+          new shaka.util.FakeEvent(shaka.ads.Utils.AD_THIRD_QUARTILE));
     });
     this.adEventManager_.listenOnce(this.player_, 'complete', complete);
     this.adEventManager_.listen(this.video_, 'play', () => {