Steps to reproduce:

1) Download attached project 'TestProject5.5.zip' and open in Unity
2) Build and run 'Test' scene on a device
3) Check profiler/logs or any other program where you can see device's memory usage

Note: You should see a small memory leak on each UnityWebRequest request which leads application to crash

Reproduced with:
5.4.4f1, 5.5.0p3, 5.6.0b2

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Fixed in: 5.6.2p1, 2017.1.0f1