At one point, I was viewing a single web page and the Chromebook was sluggish.
Many times the Chrome browser has reported that it was up to date, yet Flash was not.
GOODBYE FLASH This site (page really) started as way for me to easily find the main Adobe Flash tester page (links at the top above) which reports both on the installed copy of Flash in your browser and the latest version for assorted operating systems.
A Windows user with IE, Firefox and Chrome can have three copies of the Flash Player and each can be at a different version. For many years the update procedure for Flash was manual, rather than automatic.
Now (December 2014) that things are more automated, the problem is inconsistency.
On Windows 8, Flash in IE10 and 11 is updated with Windows Update.