Operating system: macOS Mojave 10.14.5
Graphics card: Intel Iris Pro 5200
Short description of error
When I'm working with two monitors, and there is one window with shading editor on one monitor and a window with 3D view on the other monitor; whenever I go to Cycles rendered view on the 3D viewport, the rendering gets stuck on "Initializing" stage. When I go to the window with the 3D viewport and activate it (click on the window) and shift the viewing angle a little bit to reinitialize the render, it starts working. I tried with both 2.80 and 2.81 versions, the error occurs in both. 2.79b doesn't have this problem (I use a 15" Macbook Pro Mid 2014 and have an external monitor connected to it via HDMI).
Exact steps for others to reproduce the error
Open the test file. Put the window with shader editor to the external monitor, put the window with the 3D viewport to the Macbook's main monitor. Enable rendered view on the window with 3D viewport. On the window with the shader editor, change the Scale number of the Noise Texture. It does not always get stuck, so keep changing the Scale number by sliding it with your mouse (not by typing in a value), you can also change the detail and distortion values if the problem doesn't occur. It should happen after changing the values several times.