Clear error code needed for bad MIME type in addTextTrack (#3110)

Closes #1782

lib/player.js

@@ -31,6 +31,7 @@ goog.require('shaka.media.TimeRangesUtils');
 goog.require('shaka.net.NetworkingEngine');
 goog.require('shaka.routing.Walker');
 goog.require('shaka.text.SimpleTextDisplayer');
+goog.require('shaka.text.TextEngine');
 goog.require('shaka.text.UITextDisplayer');
 goog.require('shaka.util.AbortableOperation');
 goog.require('shaka.util.ConfigUtils');
@@ -3990,6 +3991,17 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       closedCaptions: null,
     };
 
+    const fullMimeType = shaka.util.MimeUtils.getFullType(
+        stream.mimeType, stream.codecs);
+    const supported = shaka.text.TextEngine.isTypeSupported(fullMimeType);
+    if (!supported) {
+      throw new shaka.util.Error(
+          shaka.util.Error.Severity.CRITICAL,
+          shaka.util.Error.Category.TEXT,
+          shaka.util.Error.Code.MISSING_TEXT_PLUGIN,
+          mimeType);
+    }
+
     this.manifest_.textStreams.push(stream);
     this.onTracksChanged_();
     return shaka.util.StreamUtils.textStreamToTrack(stream);
@@ -4152,6 +4164,17 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
       closedCaptions: null,
     };
 
+    const fullMimeType = shaka.util.MimeUtils.getFullType(
+        stream.mimeType, stream.codecs);
+    const supported = shaka.text.TextEngine.isTypeSupported(fullMimeType);
+    if (!supported) {
+      throw new shaka.util.Error(
+          shaka.util.Error.Severity.CRITICAL,
+          shaka.util.Error.Category.TEXT,
+          shaka.util.Error.Code.MISSING_TEXT_PLUGIN,
+          mimeType);
+    }
+
     this.manifest_.textStreams.push(stream);
     this.onTracksChanged_();
     return shaka.util.StreamUtils.textStreamToTrack(stream);