Reproduction steps:
1. Download project "Test_WWW_textureNonReadable_Stutter.zip" and open in Unity
2. Select scene "Scene"
3. Disable Window -> Profiler -> Record
4. Enter Play mode
5. Press button "Button" in Game view
6. Enable Record
7. Press button "Button" in Game view

Actual: Unity freezes
Expected: image should change in Game view and Profiler should record performance data

Reproduced on: 2017.3.0a2; 2017.2.0b5; 2017.1.0p2; 2017.1.0b3
Not reproduced on: 2017.1.0b1; 5.6.3f1; 5.5.4p1
Regression introduced: 2017.1.0b2

Note: 5.6.3f1 and higher (until 2017.1.0b2) show error - "Profiler sampler Destroy exists but has a different group"