This didn't actually cause any issues because there is only one listener
for the affected methods right now. Should we have added more, the last
called observer would have overwritten `prevent_default`. Lets only set
it when necessary to avoid this footgun in the future.
* Add atom::api::TopLevelWindow
* Make BrowserWindow inherit TopLevelWindow
* Fix reading from wrong weak map
* Read options after setting content view
* OnWindowClosed is not guarenteed to run now
* Fix the offscreen hack in BrowserWindow
* Fix building on Linux
* Fix tests on Linux
* Fix building on Windows
