Note you need to scroll quite a bit down in chrome://settings/content to enable this. In the man time, nothing beats The Great Suspender: a plugin that just suspends inactive tabs to they do not use any CPU or memory at all.
Chrome will pause plugin content (e.g. Flash animations) to improve battery life: http://bit.ly/1dQj2o9 – give it a try!
“This feature will be enabled by default on Chrome’s latest desktop Beta channel release starting today, and will be rolling out soon to everyone else on Chrome desktop. If you need to manually enable it, just head to Chrome’s content settings and select ‘Detect and run important plugin content’.”