Bugzilla

### Beta/Release Uplift Approval Request
* **User impact if declined**: The CORS video subtitle couldn't be loaded correctly when user set video's prelod to `none`. It's a regression caused by bug 1313711.
* **Is this code covered by automated tests?**: Yes
* **Has the fix been verified in Nightly?**: No
* **Needs manual test from QE?**: No
* **If yes, steps to reproduce**: Visit the page in comment0 to see if subtitle can be showed correctly.
* **List of other uplifts needed**: None
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: This change is only affected on those video with preload `none` and its child track element has CORS resouce, it's not a common case. In addition, we have added an automation test for that.
* **String changes made/needed**:

### Beta/Release Uplift Approval Request
* **User impact if declined**: The CORS video subtitle couldn't be loaded correctly when user set video's prelod to `none`. It's a regression caused by bug 1313711.
* **Is this code covered by automated tests?**: Yes
* **Has the fix been verified in Nightly?**: No
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: Visit the page in comment0 to see if subtitle can be showed correctly.
* **List of other uplifts needed**: None
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: This change is only affected on those video with preload `none` and its child track element has CORS resouce, it's not a common case. In addition, we have added an automation test for that.
* **String changes made/needed**: