In the network pane of developers tools, one can right click and request "Copy All as HAR" this creates what claims to be a HAR 1.2 version file. However, the HAR 1.2 spec seems to specify an integer value in milliseconds for timings. The data created by
"blocked": 3.9859999960754067,
"dns": 0.08399999933317304,
"connect": 42.080000006535556,
"send": 0.32499999360879883,
"wait": 43.70500000368338,
"receive": 2.7791655738838017,
"ssl": 18.10000000114087
Haven't found a HAR viewer that can handle this.