Flow Events in chrome:://tracing - google-chrome

Question

I have an application that logs to a text file, which then i convert to a JSON with a script. That JSON is loaded into chrome:://tracing in Chromium.
There is documentation for the tracing format here.
I got the "simple" version with Duration Events working, but i can't figure out to log "Flow Events" (i find the documentation confusing). I've tried several ways and it either refuses the JSON as invalid, or accepts it but doesn't show any lines/arrows.
Can someone explain the format and ideally post a small example JSON of Flow Events ?

Answer 1

I managed in the following JSON to have a flow event created (and drawn) from subfunction ABTh1sF1 (40ms) to enclosing function ABTh1F1 (89ms). These nested functions are within one slice.
The flow event is also shown under "Flow events" menu.
{
"traceEvents":[
{"cpu":0,"args":{"name":"ABProcess"},"cat":"__metadata","name":"process_name","ph":"M","pid":1,"tid":0,"ts":0},
{"args":{"name":"ABThread1"},"cat":"__metadata","name":"thread_name","ph":"M","pid":1,"tid":1,"ts":0},
{"args":{},"cat":"cc2","name":"ABTh1F1","ph":"B","pid":1,"tid":1,"ts":30},
{"args":{},"cat":"cc2","name":"ABTh1sF1","ph":"B","pid":1,"tid":1,"ts":40},
{"cat": "foo", "name": "async_flow", "id":100, "ph": "s", "ts":41, "pid":1,"tid":1},
{"args":{},"cat":"cc2","name":"ABTh1sF1","ph":"E","pid":1,"tid":1,"ts":55},
{"cat": "foo", "name": "async_flow", "id":100, "ph": "f", "ts":89, "pid":1,"tid":1},
{"args":{},"cat":"cc2","name":"ABTh1F1","ph":"E","pid":1,"tid":1,"ts":90}
]
}

Answer 2

Because the other answer didn't work for me, here's another example.
Remember to enable it using the top right Flow events button.
{
"traceEvents": [
{
"cat": "example",
"name": "parent",
"ph": "B",
"pid": 1,
"tid": 1,
"ts": 0
},
{
"cat": "example",
"name": "child",
"ph": "B",
"pid": 1,
"tid": 2,
"ts": 25
},
{
"cat": "example",
"name": "flow",
"id": 100,
"ph": "s",
"ts": 0,
"pid": 1,
"tid": 1
},
{
"cat": "example",
"name": "child",
"ph": "E",
"pid": 1,
"tid": 2,
"ts": 75
},
{
"cat": "example",
"name": "flow",
"id": 100,
"ph": "f",
"bp": "e",
"ts": 25,
"pid": 1,
"tid": 2
},
{
"cat": "example",
"name": "parent",
"ph": "E",
"pid": 1,
"tid": 1,
"ts": 100
}
]
}