Particle batching breaks if a particle's nested particle (be it a sub emitter or just a child) is using a different material.

Repro steps:
1. Open Particles scene from attached project.
2. Press play.
3. Observe batches in inspector.

Expected outcome: particles to batch for each material (i.e. 2 batches for whole scene).

Notes:
- not a regression; happens in 5.1.0f3 (before batching was discontinued in favor of multithreading)
- occurs also in the batch fix backports:

Version 5.4.0b10 (b83774801f70)
Wed, 09 Mar 2016 14:27:39 GMT
Branch: 5.4/particle-bugfixes

and

Version 5.3.3f1 (6f5aca424f44)
Thu, 10 Mar 2016 09:49:34 GMT
Branch: 5.3/particle-bugfixes