fix(HLS): Allow get better segment size estimations (#9043)

Related to #9041

Author: avelad

lib/hls/hls_parser.js

@@ -4349,12 +4349,20 @@ shaka.hls.HlsParser = class {
             bitrate,
             duration: reference.endTime - reference.startTime,
           });
+          reference.bandwidth = bitrate;
         } else if (bitrates.length) {
           // It applies to every segment between it and the next EXT-X-BITRATE,
           // so we use the latest bitrate value
           const prevBitrate = bitrates.pop();
           prevBitrate.duration += reference.endTime - reference.startTime;
           bitrates.push(prevBitrate);
+          reference.bandwidth = prevBitrate.bitrate;
+        }
+
+        if (reference.bandwidth) {
+          for (const partial of reference.partialReferences) {
+            partial.bandwidth = reference.bandwidth;
+          }
         }
 
         previousReference = reference;

lib/media/segment_reference.js

@@ -407,9 +407,14 @@ shaka.media.SegmentReference = class {
   getSize() {
     if (this.endByte) {
       return this.endByte - this.startByte;
-    } else {
-      return null;
     }
+    if (this.bandwidth) {
+      const size = this.bandwidth * (this.endTime - this.startTime);
+      if (!isNaN(size) && size > 0) {
+        return size;
+      }
+    }
+    return null;
   }
 
   /**