Prerequisites:
For repro you will need an external display and OSX system.

Steps to repro:

1. Open Unity on OSX;
2. Open attached project and 'test' scene;
3. Open Profiler window (Window -> Profiler);
4. Move Profile window to the external display;
5. Enter Play mode;
6. Observe Canvas gameobject (both Scene and Game views).

Actual result:
Canvas with all its contains (images, texts) starts flickering when Profiler window is moved to the external window (see attached gif video).
Regression introduced in Unity 5.4.

Expected result:
Canvas should not flicker when moving Profiler window to the external display.

Workaround is to launch Profiler at the same display as Editor.

Notes:
- Reproducible on: 5.4.0b12, 5.4.0b11, 5.4.0b7;
- Reproducible on OSX 10.11.3;
- Not reproducible in 2018.3.0a1 on OSX 10.13.4
- Not reproducible in 5.3.4p1, 5.3.4f1, 5.3.3.f1;
- Not reproducible on Windows 10 and 8.1;
- Reproduces only in Editor; doesn't repro in standalone build.