[css-grid] Fix definite/indefinite size detection for abspos elements
This is a port from Blink: https://codereview.chromium.org/1383003002
Created attachment 276720 [details]
Comment on attachment 276720 [details]
Removing from the review queue as there're some discussion on the CSS WG about the expected behaviour:
It should be resolved in the next F2F meeting (9-11 May).