UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36

Example URL:
http://mba.illinois.edu, http://beholdisrael.org

Steps to reproduce the problem:
1. load page in chrome (or Canary) with devtools open.
2. observe background video playback (~1 minute) 
3. When video begins loop - rather than read from cache, the video is downloaded again from the server.  This can repeat many times, adding a large amount of tonnage to page load

What is the expected behavior?
Expected behaviour is that the video is cached and only read from the cache.  This is seen in Firefox, Brave and Safari, but reproducible in Chrome and Canary.

What went wrong?
It appears that very large videos on webpages are being kicked out of the cache before they can be reused on the same page load.  This results in the videos being downloaded over and over, as long as the page is open.  I can reproduce on my computer, and also with WebPageTest:

https://www.webpagetest.org/result/181117_B4_d3f963f1b9b74359bdff99d993df31cb/
https://www.webpagetest.org/result/181117_N1_d02398187dec9eee8ecaa042766d3712/

Did this work before? N/A 

Chrome version: 70.0.3538.102  Channel: n/a
OS Version: OS X 10.13.6
Flash Version: