* you can share the original URL
* you can share the URL of a simplified demo of the problem
* you can test if it's fixed in Chrome Canary
* you can bisect the regression yourself:
  https://www.chromium.org/developers/bisect-builds-py

Unfortunately I can't use Chrome Canary since my project is being built within Linux.

the contents of the page are supplied by a server.  I could just run it live. Seems a lot of trouble though to set it all up.

The previous version of Chrome that worked was the one right before this latest one.  67.0.3396.79

One additional side not.  May help weed out the source of the problem.  Previously on previous Chrome builds the page would load, and then after 30 seconds the performance would drop significantly.  I'd refresh the page and then the content would load back up and the problem would be gone for good.  Now the problem happens regardless of the number of times I refresh the page.

This seems to be the very function that is causing the bottleneck.  Any ideas why?
copyVector3sArray:
function(a)
{
	for(var b=this.array,c=0,d=0,e=a.length;d<e;d++)
		{
			var f=a[d];
			void 0===f&&(console.warn("THREE.BufferAttribute.copyVector3sArray(): vector is undefined",d),f=new n);
			b[c++]=f.x;
			b[c++]=f.y;
			b[c++]=f.z
		}

	return this
}

the size of the array it is copying is 468000 in length

Without a demo there's nothing for the Chromium team to go on, I'm afraid.
Try bisecting yourself using the link I gave in comment 1.

I thought bisecting only determines which version the change occurs in?

Well, here's another screen shot

this.length is 468000, and a.length is 156000.

Deleted: Screenshot from 2018-08-03 14-10-12.png 496 KB

	Screenshot from 2018-08-03 14-10-12.png 496 KB View Download

Are there perhaps new memory limitations imposed now?  I know my project uses up a lot of RAM, could that be causing issues for these particular arrays that are being copied?

Bisecting produces a list of commits (usually 1-20) so it's usually obvious which change caused the regression. This is a much more reliable way to determine the reason compared to guessing. I don't think Chromium team would guess without being able to reproduce the problem as there are lots of cases where the reported problems are caused by something else.

reporter@ - Thanks for filing the issue...!!

Could you please provide a sample test file/url to test the issue from TE-end.
This will help us in triaging the issue further.

Thanks...!!

Closing bug because it can't be reproduced. Please reopen if you are able to provide a reproducible test case :)

The NextAction date has arrived: 2018-08-27