Windows 8.1, IE11, laptop flow. See #16143.
Start on the front end.
Admin bar -> site title -> Customize.
Customizer opens. Click “Site Identity” (formerly Site Title and Tagline).
Click change image.
Media Modal opens. Select an image.
Click Select and Crop.
Cropper opens. Adjust the handles.
Modal closes, new cropped icon shows up in Customizer controls, and favicon is updated in the browser.