Fix SegmentTemplate w/ duration for live

When calculating segment references, the end time should be capped at
the period's end, except when the period has no end.

Closes #1204

Change-Id: Ia608452706bbc3fd847a645197e8a0cb57d7aaec

lib/dash/segment_template.js

@@ -335,7 +335,8 @@ shaka.dash.SegmentTemplate.createFromDuration_ = function(context, info) {
         position * segmentDuration - scaledPresentationTimeOffset;
     // Cap the segment end at the period end, to avoid period transition issues
     // in StreamingEngine.
-    var segmentEnd = Math.min(segmentStart + segmentDuration, periodDuration);
+    var segmentEnd = segmentStart + segmentDuration;
+    if (periodDuration) segmentEnd = Math.min(segmentEnd, periodDuration);
 
     // Do not construct segments references that should not exist.
     if (segmentEnd < 0)

test/dash/dash_parser_live_unit.js

@@ -1000,6 +1000,29 @@ describe('DashParser Live', function() {
         basicLines, basicRefs, updateLines, updateRefs, partialUpdateLines);
   });
 
+  describe('SegmentTemplate w/ duration', function() {
+    var templateLines = [
+      '<SegmentTemplate startNumber="1" media="s$Number$.mp4" duration="2" />'
+    ];
+
+    it('produces sane references without assertions', function(done) {
+      var manifest = makeSimpleLiveManifestText(templateLines, updateTime);
+
+      fakeNetEngine.setResponseMapAsText({'dummy://foo': manifest});
+      parser.start('dummy://foo', playerInterface).then(function(manifest) {
+        expect(manifest.periods.length).toBe(1);
+        var stream = manifest.periods[0].variants[0].video;
+
+        // In https://github.com/google/shaka-player/issues/1204, this
+        // failed an assertion and returned endTime == 0.
+        var ref = stream.getSegmentReference(1);
+        expect(ref.endTime).toBeGreaterThan(0);
+      }).catch(fail).then(done);
+      shaka.polyfill.Promise.flush();
+    });
+  });
+
+
   describe('EventStream', function() {
     /** @const */
     var originalManifest = [