Resolve thread button is missing when polling for notes that were transformed into threads

When our polling endpoint receives a reply that transforms the parent into a thread, the "Resolve thread" at the bottom is missing.

Steps to reproduce

  1. On an MR, create a regular comment (not a thread).
  2. Open this MR in two tabs.
  3. On the first tab, reply to this comment to turn this into a thread.
  4. On the second tab, notice that the "Resolve thread" button is missing.

Screen_Shot_2020-10-02_at_9.00.14_PM

Note that the parent note was actually marked as resolvable because you can see the small check mark appearing there. But I think some state for the reply field is not updated.

Expected:

Screen_Shot_2020-10-02_at_9.01.23_PM

Also, this part is not updated:

Screen_Shot_2020-10-02_at_9.02.21_PM