Chrome Version       : 67.0.3396.62
OS Version: OS X 10.13.4
URLs (if applicable) : occurs on e.g. inbox.google.com, photos.google.com, but also seemingly random ads frames or other web pages
Other browsers tested: n/a

What steps will reproduce the problem?
1. Use Chrome 67 to browse
2. Notice your notebooks fan spinning
3. Using task manager, find that some tab uses 100% CPU

Killing the process that runs the particular tab and then reloading fixes the issue temporarily, but it does come back eventually. I took a JavaScript CPU profile, but that has no activity showing.

UserAgentString: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.62 Safari/537.36