Nested child transition not working

[JouanMarcel]

Version

2.5.21

Reproduction link

https://jsfiddle.net/365deb40/

Steps to reproduce

Click the app container to toggle whether the two colored containers are shown or not

What is expected?

Transitions for both elements (rotating and fading)

What is actually happening?

Only the parent (primary / fade) transition is showing

---

Try removing the first transition and the v-if attribute of the parent element, to see that the second transition is working fine on its own.

  <section>
      <div class="primary" key="primary">
        <transition name="rotate" mode="out-in">
          <div class="secondary" v-if="show" key="secondary"></div>
        </transition>
      </div>
  </section>

[posva]

Duplicated of #7643