If you want to test out ES2015 features (incl. proxies) coming soon in V8, you can download Chrome Canary and turn on the Experimental JavaScript flag (under chrome://flags). With the flag enabled, Chrome reaches 91% percent on the Kangax table [0]. We're working hard to turn these features on by default as soon as possible.

[0]: https://kangax.github.io/compat-table/es6/

(Disclaimer: I'm a PM on the V8 team)