Now Google+ Hangouts no longer requires plugins in Chrome. Google uses WebRTC and Native Client to provide a native video chat experience.
"We're rolling out an update that makes it easier than ever to start Hangouts video calls with your family and friends! You'll now be able to launch Hangouts in Chrome without having to download and install a plugin. Just click to start the Hangout, allow Hangouts to use your camera and microphone, and you'll be good to go! This update is now available for all Chrome Dev and Canary users, and will be rolling out to all Chrome users over the next few weeks."
You can get a list of the plugins currently used by Chrome by visiting chrome://plugins (an internal Chrome page). The page lets you disable some of the plugins or whitelist them: check "always allowed" to disable Chrome's plugin blocking feature. Some of the plugins are bundled with Chrome and use Google's PPAPI/Pepper instead of NPAPI: Chrome Remote Desktop Viewer, Widevine Content Decryption Module, Adobe Flash Player, Chrome PDF Viewer, Native Client.