It's a really piece of cake to do this. It's using grease monkey script that used in Firefox. Now, we're going to use it in Chrome or Chromium browser, that at least version 4.0 or higher.
1. Go to the Youtube userscript.org page http://userscripts.org/scripts/show/25105. Then click the "Install Button".
2.You will notice that there is confirmation to install extension. Clik "Continue" to install.
notification will appear shortly.
Now, go to Youtube video page. Let it loaded properly until you see the "Download" button appear between the "Embed" and "Flag" button. Click it, and choose which video resolution you want. Remember, the bigger resolution is, the better video quality would be.
