feat(text): Add time context to modifyCueCallback

externs/shaka/text.js

@@ -87,9 +87,11 @@ shaka.extern.TextParser.TimeContext;
 
 /**
  * A callback used for editing cues before appending.
- * Provides the cue, and the URI of the captions file the cue was parsed from.
+ * Provides the cue, the URI of the captions file the cue was parsed from, and
+ * the time context that was used when generating that cue.
  * You can edit the cue object passed in.
- * @typedef {function(!shaka.text.Cue, ?string)}
+ * @typedef {function(!shaka.text.Cue, ?string,
+ *    !shaka.extern.TextParser.TimeContext)}
  * @exportDoc
  */
 shaka.extern.TextParser.ModifyCueCallback;

lib/text/text_engine.js

@@ -209,7 +209,7 @@ shaka.text.TextEngine = class {
     const allCues = this.parser_.parseMedia(
         shaka.util.BufferUtils.toUint8(buffer), time, uri);
     for (const cue of allCues) {
-      this.modifyCueCallback_(cue, uri || null);
+      this.modifyCueCallback_(cue, uri || null, time);
     }
     const cuesToAppend = allCues.filter((cue) => {
       return cue.startTime >= this.appendWindowStart_ &&

test/text/text_engine_unit.js

@@ -144,8 +144,10 @@ describe('TextEngine', () => {
           shaka.test.Util.spyFunc(modifyCueCallback));
       mockParseMedia.and.returnValue([cue1, cue2]);
       await textEngine.appendBuffer(dummyData, 0, 3, 'uri');
-      expect(modifyCueCallback).toHaveBeenCalledWith(cue1, 'uri');
-      expect(modifyCueCallback).toHaveBeenCalledWith(cue2, 'uri');
+      expect(modifyCueCallback).toHaveBeenCalledWith(
+          cue1, 'uri', jasmine.objectContaining({periodStart: 0}));
+      expect(modifyCueCallback).toHaveBeenCalledWith(
+          cue2, 'uri', jasmine.objectContaining({periodStart: 0}));
     });
   });