UserAgent: Mozilla/5.0 (X11; CrOS x86_64 9901.77.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.97 Safari/537.36
Platform: 9901.77.0 (Official Build) stable-channel caroline

Steps to reproduce the problem:
1. I'm not sure how to reproduce specifically.
2. I am running a requestAnimationFrame loop, and sometimes the call stack is empty (see screenshots).
3. Try recording this codepen and you may see empty frame stacks: https://s.codepen.io/trusktr/debug/rpaQqK

What is the expected behavior?
I would expect to see all call stacks for every frame.

What went wrong?
Sometimes call stacks don't appear in the timeline.

Did this work before? N/A 

Chrome version: 62.0.3202.97  Channel: stable
OS Version: 9901.77.0
Flash Version: 

One screenshot shows a completely empty frame, which shouldn't actually be the case because my code is like this:

```
requestAnimationFrame(function loop() {
  // ... do stuff ...
  requestAnimationFrame(loop)
})
```

so based on a render loop like that we should never see a frame with no call stack.

The other screenshot shows that half the frame's callstack is missing, which shouldn't happen because the function call that I see should only happen if the stuff in the first half triggers it, so if there's no first half, there shouldn't even be a frame at all in fact.

Something seems wrong with a frame being completely empty, which may have to do with the frame that has only half the callstack showing, though it's possible the half-callstack incidents might be my own issue (I'm not 100% sure yet).
 

Deleted: Screenshot 2018-01-01 at 6.17.03 PM.png 368 KB

	Screenshot 2018-01-01 at 6.17.03 PM.png 368 KB View Download

Deleted: Screenshot 2018-01-01 at 6.18.09 PM.png 363 KB

	Screenshot 2018-01-01 at 6.18.09 PM.png 363 KB View Download