Fix FilteringHlsPlaylistParser

Only filter HlsMasterPlaylists.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=183394956

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/offline/HlsDownloadAction.java

@@ -26,7 +26,8 @@ import java.io.IOException;
 /** An action to download or remove downloaded HLS streams. */
 public final class HlsDownloadAction extends SegmentDownloadAction<String> {
 
-  public static final Deserializer DESERIALIZER = new SegmentDownloadActionDeserializer<String>() {
+  public static final Deserializer DESERIALIZER =
+      new SegmentDownloadActionDeserializer<String>() {
 
         @Override
         public String getType() {
@@ -40,15 +41,14 @@ public final class HlsDownloadAction extends SegmentDownloadAction<String> {
 
         @Override
         protected String[] createKeyArray(int keyCount) {
-      return new String[0];
+          return new String[keyCount];
         }
 
         @Override
-    protected DownloadAction createDownloadAction(Uri manifestUri, boolean removeAction,
-        String data, String[] keys) {
+        protected DownloadAction createDownloadAction(
+            Uri manifestUri, boolean removeAction, String data, String[] keys) {
           return new HlsDownloadAction(manifestUri, removeAction, data, keys);
         }
-
       };
 
   private static final String TYPE = "HlsDownloadAction";