From 0f57341e38e921dc2a652d6d72fb5deded7a8793 Mon Sep 17 00:00:00 2001
From: Gary Katsevman <git@gkatsev.com>
Date: Thu, 2 Mar 2017 11:16:12 -0500
Subject: [PATCH] fix(cues): only copy cue props that don't exist (#4145)

---
 src/js/tracks/text-track.js         |  4 +++-
 test/unit/tracks/text-track.test.js | 12 +++++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/js/tracks/text-track.js b/src/js/tracks/text-track.js
index 4f17142bf..228a423ed 100644
--- a/src/js/tracks/text-track.js
+++ b/src/js/tracks/text-track.js
@@ -343,7 +343,9 @@ class TextTrack extends Track {
       cue = new window.vttjs.VTTCue(originalCue.startTime, originalCue.endTime, originalCue.text);
 
       for (const prop in originalCue) {
-        cue[prop] = originalCue[prop];
+        if (!(prop in cue)) {
+          cue[prop] = originalCue[prop];
+        }
       }
     }
 
diff --git a/test/unit/tracks/text-track.test.js b/test/unit/tracks/text-track.test.js
index c98907839..aaed0bbb0 100644
--- a/test/unit/tracks/text-track.test.js
+++ b/test/unit/tracks/text-track.test.js
@@ -19,7 +19,17 @@ const defaultTech = {
   currentTime() {}
 };
 
-QUnit.module('Text Track');
+QUnit.module('Text Track', {
+  beforeEach() {
+    this.oldVttjs = window.vttjs;
+    window.vttjs = {
+      VTTCue: Object
+    };
+  },
+  afterEach() {
+    window.vttjs = this.oldVttjs;
+  }
+});
 
 // do baseline track testing
 TrackBaseline(TextTrack, {