Add AdsLoader.focusSkipButton()

This method allows to call through to `StreamManager.focus()` of the currently playing SSAI stream.

PiperOrigin-RevId: 501399144
(cherry picked from commit 0ba0c0ed)

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaServerSideAdInsertionMediaSource.java

@@ -374,8 +374,7 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
 
     private final ServerSideAdInsertionConfiguration configuration;
     private final Context context;
-    private final Map<ImaServerSideAdInsertionMediaSource, MediaSourceResourceHolder>
-        mediaSourceResources;
+    private final Map<String, MediaSourceResourceHolder> mediaSourceResources;
     private final Map<String, AdPlaybackState> adPlaybackStateMap;
 
     @Nullable private Player player;
@@ -402,6 +401,35 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
     }
 
     /**
+     * Puts the focus on the skip button, if a skip button is present and an ad is playing.
+     *
+     * @see StreamManager#focus()
+     */
+    public void focusSkipButton() {
+      if (player == null) {
+        return;
+      }
+      if (player.getPlaybackState() != Player.STATE_IDLE
+          && player.getPlaybackState() != Player.STATE_ENDED
+          && player.getMediaItemCount() > 0) {
+        int currentPeriodIndex = player.getCurrentPeriodIndex();
+        Object adsId =
+            player
+                .getCurrentTimeline()
+                .getPeriod(currentPeriodIndex, new Timeline.Period())
+                .getAdsId();
+        if (adsId instanceof String) {
+          MediaSourceResourceHolder mediaSourceResourceHolder = mediaSourceResources.get(adsId);
+          if (mediaSourceResourceHolder != null
+              && mediaSourceResourceHolder.imaServerSideAdInsertionMediaSource.streamManager
+                  != null) {
+            mediaSourceResourceHolder.imaServerSideAdInsertionMediaSource.streamManager.focus();
+          }
+        }
+      }
+    }
+
+    /**
      * Releases resources.
      *
      * @return The {@link State} that can be used when resuming from the background.
@@ -427,7 +455,7 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
         StreamPlayer streamPlayer,
         com.google.ads.interactivemedia.v3.api.AdsLoader adsLoader) {
       mediaSourceResources.put(
-          mediaSource, new MediaSourceResourceHolder(mediaSource, streamPlayer, adsLoader));
+          mediaSource.adsId, new MediaSourceResourceHolder(mediaSource, streamPlayer, adsLoader));
     }
 
     private AdPlaybackState getAdPlaybackState(String adsId) {