1811071 - action.openPopup / browserAction.openPopup should resolve promise after showing popup

Status: NEW

(WebExtensions :: General, enhancement, P3)

Description

[Rob Wu [:robwu]]

Currently, browserAction.openPopup() resolves as soon as the popup opening process has commenced.
In contrast, Chrome waits for the content to have been loaded & popup to have been displayed before resolving the promise: https://bugs.chromium.org/p/chromium/issues/detail?id=1245093#c13

If we update the method to delay the promise resolution until the completion of the popup load, then it would become easier for extensions (and unit tests...) to interact with the opened popup. A cause of intermittent test failures is that a test may already be closing the popup or window while it was still in the process of being displayed.