AudioStream: remove unused youtube-specific fields

These fields were added in
TeamNewPipe#810 in
preparation for a DASH support that never materialized … well it did
materialize, but did not use any of these variables.

Since they are youtube-specific, it does not make much sense to export
them in the generic API, lest people start depending on them as if
they belonged to all backends.

Well, 4 variables are actually already depended on in places, they
will have to be checked separately. But this is the low-hanging fruit.

extractor/src/main/java/org/schabi/newpipe/extractor/stream/AudioStream.java

@@ -33,13 +33,7 @@ public final class AudioStream extends Stream {
 
     private final int averageBitrate;
 
-    // Fields for DASH
-    private int itag = ITAG_NOT_AVAILABLE_OR_NOT_APPLICABLE;
-    private int bitrate;
-    private int initStart;
-    private int initEnd;
-    private int indexStart;
-    private int indexEnd;
+    // Fields specific to the Youtube backend
     private String quality;
     private String codec;
 
@@ -348,14 +342,7 @@ private AudioStream(@Nonnull final String id,
                         @Nullable final ItagItem itagItem) {
         super(id, content, isUrl, format, deliveryMethod, manifestUrl);
         if (itagItem != null) {
-            this.itagItem = itagItem;
-            this.itag = itagItem.id;
             this.quality = itagItem.getQuality();
-            this.bitrate = itagItem.getBitrate();
-            this.initStart = itagItem.getInitStart();
-            this.initEnd = itagItem.getInitEnd();
-            this.indexStart = itagItem.getIndexStart();
-            this.indexEnd = itagItem.getIndexEnd();
             this.codec = itagItem.getCodec();
         }
         this.averageBitrate = averageBitrate;
@@ -386,88 +373,6 @@ public int getAverageBitrate() {
         return averageBitrate;
     }
 
-    /**
-     * Get the itag identifier of the stream.
-     *
-     * <p>
-     * Always equals to {@link #ITAG_NOT_AVAILABLE_OR_NOT_APPLICABLE} for other streams than the
-     * ones of the YouTube service.
-     * </p>
-     *
-     * @return the number of the {@link ItagItem} passed in the constructor of the audio stream.
-     */
-    public int getItag() {
-        return itag;
-    }
-
-    /**
-     * Get the bitrate of the stream.
-     *
-     * @return the bitrate set from the {@link ItagItem} passed in the constructor of the stream.
-     */
-    public int getBitrate() {
-        return bitrate;
-    }
-
-    /**
-     * Get the initialization start of the stream.
-     *
-     * @return the initialization start value set from the {@link ItagItem} passed in the
-     * constructor of the stream.
-     */
-    public int getInitStart() {
-        return initStart;
-    }
-
-    /**
-     * Get the initialization end of the stream.
-     *
-     * @return the initialization end value set from the {@link ItagItem} passed in the constructor
-     * of the stream.
-     */
-    public int getInitEnd() {
-        return initEnd;
-    }
-
-    /**
-     * Get the index start of the stream.
-     *
-     * @return the index start value set from the {@link ItagItem} passed in the constructor of the
-     * stream.
-     */
-    public int getIndexStart() {
-        return indexStart;
-    }
-
-    /**
-     * Get the index end of the stream.
-     *
-     * @return the index end value set from the {@link ItagItem} passed in the constructor of the
-     * stream.
-     */
-    public int getIndexEnd() {
-        return indexEnd;
-    }
-
-    /**
-     * Get the quality of the stream.
-     *
-     * @return the quality label set from the {@link ItagItem} passed in the constructor of the
-     * stream.
-     */
-    public String getQuality() {
-        return quality;
-    }
-
-    /**
-     * Get the codec of the stream.
-     *
-     * @return the codec set from the {@link ItagItem} passed in the constructor of the stream.
-     */
-    public String getCodec() {
-        return codec;
-    }
-
     /**
      * Get the id of the audio track.
      *