Trigger the event 'problematicFocusDetected' more appropriately
Trigger the event 'problematicFocusDetected' more appropriately

This avoids some cases of false alarms caused by previous change for
https://github.com/webextensions/live-css-editor/issues/4

Before this change, if the code execution was temporarily paused in
debug mode, it could lead to false alarms for
'problematicFocusDetected'.

webextensions/live-css-editor,webextensions/live-css-editor,webextensions/live-css-editor