Fix display order of cues with identical ranges

Since the browser displays identical ranges from bottom up, we must
reverse the order before feeding them to the browser.  This way, the
first one parsed shows up on top.

Issue #848

Backported to v2.1.x

lib/media/text_engine.js

@@ -172,6 +172,10 @@ shaka.media.TextEngine.prototype.appendBuffer =
     // Parse the buffer and add the new cues.
     var cues = this.parser_.parseMedia(buffer, time);
 
+    // Reverse the order so that display of line=auto is correct.
+    // https://github.com/google/shaka-player/issues/848
+    cues.reverse();
+
     for (var i = 0; i < cues.length; ++i) {
       if (cues[i].startTime >= this.appendWindowEnd_) break;
       this.track_.addCue(cues[i]);

test/media/text_engine_unit.js

@@ -114,6 +114,18 @@ describe('TextEngine', function() {
       }).catch(fail).then(done);
     });
 
+    it('adds cues in reverse order', function(done) {
+      // Regression test for https://github.com/google/shaka-player/issues/848
+      mockParseMedia.and.returnValue([1, 2, 3]);
+      textEngine.appendBuffer(dummyData, 0, 3).then(function() {
+        expect(mockTrack.addCue.calls.count()).toBe(3);
+        var calls = mockTrack.addCue.calls;
+        expect(calls.argsFor(0)).toEqual([3]);
+        expect(calls.argsFor(1)).toEqual([2]);
+        expect(calls.argsFor(2)).toEqual([1]);
+      }).catch(fail).then(done);
+    });
+
     it('does not throw if called right before destroy', function(done) {
       mockParseMedia.and.returnValue([1, 2, 3]);
       textEngine.appendBuffer(dummyData, 0, 3).catch(fail).then(done);