Fix ImaAdsLoaderTest

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213824217

extensions/ima/src/test/java/com/google/android/exoplayer2/ext/ima/FakePlayer.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.ext.ima;
 
+import android.os.Looper;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Timeline;
@@ -111,6 +112,11 @@ import java.util.ArrayList;
   // ExoPlayer methods. Other methods are unsupported.
 
   @Override
+  public Looper getApplicationLooper() {
+    return Looper.getMainLooper();
+  }
+
+  @Override
   public void addListener(Player.EventListener listener) {
     listeners.add(listener);
   }