Operating system: Darwin-18.7.0-x86_64-i386-64bit 64 Bits
Graphics card: Intel(R) Iris(TM) Plus Graphics 655 Intel Inc. 4.1 INTEL-12.10.12
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Short description of error
When a 3D viewport/UV editor are on separate screens, the render view will hang on "Initializing," and doesn't not recover until all UV editors and 3D viewports are on the same screen.
Upon moving the editors to the same screen (or closing them), then switching from rendered view to another view, and back to rendered view, the scene begins to render.
Exact steps for others to reproduce the error
[Notes: This works with the startup file, has not been tested with GPU, and am using a thunderbolt 3 to HDMI adapter to the second display]
Open any project, add a new window, put one window on one monitor with another window on the other, ensure that both windows have either the UV editor or 3D viewport (one must have the 3D viewport to enable rendered view on), switch to cycles, and enable rendered view on either of the two monitors.