fix(HLS): Fix bandwidth detection (shaka-project#9230)

Previously, AVERAGE-BANDWIDTH was prioritized over BANDWIDTH, but this
produces undesirable results when peaks are reproduced and the ABR is
unable to act.

Author: avelad

lib/hls/hls_parser.js

@@ -1842,8 +1842,8 @@ shaka.hls.HlsParser = class {
 
       const frameRate = firstTag.getAttributeValue('FRAME-RATE');
       const bandwidth =
-          Number(firstTag.getAttributeValue('AVERAGE-BANDWIDTH')) ||
-          Number(firstTag.getRequiredAttrValue('BANDWIDTH'));
+          Number(firstTag.getRequiredAttrValue('BANDWIDTH')) ||
+          Number(firstTag.getAttributeValue('AVERAGE-BANDWIDTH'));
 
       const resolution = firstTag.getAttributeValue('RESOLUTION');
       const [width, height] = resolution ? resolution.split('x') : [null, null];

test/hls/hls_parser_unit.js

@@ -374,10 +374,10 @@ describe('HlsParser', () => {
     expect(actual).toEqual(manifest);
   });
 
-  it('prioritize AVERAGE-BANDWIDTH to BANDWIDTH', async () => {
+  it('fallback to AVERAGE-BANDWIDTH', async () => {
     const master = [
       '#EXTM3U\n',
-      '#EXT-X-STREAM-INF:BANDWIDTH=200,CODECS="avc1",',
+      '#EXT-X-STREAM-INF:BANDWIDTH=0,CODECS="avc1",',
       'RESOLUTION=960x540,FRAME-RATE=60,',
       'AVERAGE-BANDWIDTH=100\n',
       'video\n',