fix(DASH): Support "forced-subtitle" role (shaka-project#3807)

Previously, Shaka Player only supported "forced_subtitle",
which was the working name before the role was finalized.

Closes shaka-project#3767

lib/dash/dash_parser.js

@@ -1230,8 +1230,10 @@ shaka.dash.DashParser = class {
 
     let forced = false;
     if (isText) {
-      // See: https://github.com/google/shaka-player/issues/2122
-      forced = roles.includes('forced_subtitle');
+      // See: https://github.com/google/shaka-player/issues/2122 and
+      // https://github.com/Dash-Industry-Forum/DASH-IF-IOP/issues/165
+      forced = roles.includes('forced_subtitle') ||
+          roles.includes('forced-subtitle');
     }
 
     let tilesLayout;

test/dash/dash_parser_manifest_unit.js

@@ -1874,7 +1874,7 @@ describe('DashParser Manifest', () => {
     expect(textStream.kind).toBe('caption');
   });
 
-  it('converts Roles element to "forced"', async () => {
+  it('converts Roles element to "forced" (old role)', async () => {
     const manifestText = [
       '<MPD minBufferTime="PT75S">',
       '  <Period id="1" duration="PT30S">',
@@ -1906,6 +1906,38 @@ describe('DashParser Manifest', () => {
     expect(textStream.forced).toBe(true);
   });
 
+  it('converts Roles element to "forced"', async () => {
+    const manifestText = [
+      '<MPD minBufferTime="PT75S">',
+      '  <Period id="1" duration="PT30S">',
+      '    <AdaptationSet id="1" contentType="text">',
+      '      <Accessibility schemeIdUri="urn:mpeg:dash:role:2011" ',
+      '          value="captions" />',
+      '      <Accessibility schemeIdUri="urn:mpeg:dash:role:2011" ',
+      '          value="forced-subtitle" />',
+      '      <Accessibility schemeIdUri="foobar" value="bar" />',
+      '      <Representation id="text-en" mimeType="text/webvtt">',
+      '        <BaseURL>t-en.vtt</BaseURL>',
+      '      </Representation>',
+      '    </AdaptationSet>',
+      '    <AdaptationSet id="1" mimeType="video/mp4">',
+      '      <Representation id="video-sd" width="640" height="480">',
+      '        <BaseURL>v-sd.mp4</BaseURL>',
+      '        <SegmentBase indexRange="100-200" />',
+      '      </Representation>',
+      '    </AdaptationSet>',
+      '  </Period>',
+      '</MPD>',
+    ].join('\n');
+
+    fakeNetEngine.setResponseText('dummy://foo', manifestText);
+    /** @type {shaka.extern.Manifest} */
+    const manifest = await parser.start('dummy://foo', playerInterface);
+    const textStream = manifest.textStreams[0];
+    expect(textStream.roles).toEqual(['captions', 'forced-subtitle']);
+    expect(textStream.forced).toBe(true);
+  });
+
   it('supports HDR signaling via profiles', async () => {
     // (DASH-IF IOP v4.3 10.3.3.)
     const hdrProfile =