Particle CPU cost highly increase at second "show" of a streaming level.

It seems that Particle CPU cost highly increase at second "show" of a streaming level.
The Licensee's team sent a sample to reproduce this problem.
So I put the project and wrote how to reproduce on this thread.

1. Open attached project.
2. Press 1 to toggle stat unitgraph and particles
3. Press 2 to load a streaming level that has a emitter of mesh particle.
4. Press 3 to show the sublevel.
5. Press 4 to hide the sublevel.
6. Press 3 to show the sublevel again.
7. You can see the stat graph and some particle counters increase more than at the first time "show".

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