I use cVim on Chrome for all of my work computers, and DWB[0] on my personal (Linux) computer. DWB is the best in-browser Vim experience I've had, and quite light on resources in my experience.

[0]http://portix.bitbucket.org/dwb/

Vimperator for Firefox[1] and Vrome for Chrome[2] try to fulfill this ideal without changing the current browsing experience too much. You should give them a try. They are very refreshing and may be what you're looking for beyond "It's all text" 'vim-in-textareas-only' functionality.

[1] https://addons.mozilla.org/en-us/firefox/addon/vimperator/

[2] https://chrome.google.com/webstore/detail/vrome/godjoomfiimi...

From the same author: https://github.com/ardagnir/pterosaur

I want "Full vim in gmail" Every time when I want to move the cursor in the browser's editor, I type esc and then hjkl...

pentadactyl is the best vim in browser experience I've had. Hands down better than vimperator and vimium last I've used them.