To provide more context: We have strong reasons to believe that Chrome uses "too much" CPU to display ads. It general, Chrome consumes ~2x as many CPU cycles as Safari idling on web-pages with ads. Removing the ads drops both browsers to minimal CPU consumption. 
https://docs.google.com/document/d/1YVO9FGRBF1RUsedU28H6P8lt9bDpOci0vi0CLSkFih8/edit?userstoinvite=massaroemail@gmail.com&ts=584af1c9&actionButton=1#

There are several efforts that may alleviate this issue:
  * Timer throttling for hidden frames: https://bugs.chromium.org/p/chromium/issues/detail?id=616519#c39
  * Purge and suspend for background renderers: https://bugs.chromium.org/p/chromium/issues/detail?id=635419

We should:
  * Isolate an ad that is known to cause high CPU consumption on an idle page.
  * Craft a deterministic test page with this ad that shows the same symptoms.
  * Investigate and measure effects of timer throttling, purge & suspend, etc.