This was originally discussed in https://chromium-review.googlesource.com/c/chromium/src/+/1160161. reillyg@ at one point asked if it was possible to change third_party/WebKit/LayoutTests/http/tests/devtools/device-orientation-success.js to catch a "deviceorientation" event after reloading the page to assert the values passed to setDeviceOrientationOverride() were being used.

Registering a listener, however, causes "deviceorientation" events to be delivered with alpha, beta and gamma set to null. We need to find out what's causing the actual values to be lost.