I just noticed the ResizeObserver implementation in Chromium right now will fire the observation when an element changes from non-inline to inline.

Example:
http://jsbin.com/zoyupajaje/1/edit?html,js,console,output

I'm using the build from latest Chromium repository and change 'ResizeObserver status' in RuntimeEnabledFeatures.in so I can use ResizeObserver.

I think we really need to add the test case for this to test/notify.html