V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page: https://github.com/v8/v8/wiki

Checkout depot tools, and run

 fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

 git pull origin
 gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

 fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
 fetch = +refs/tags/*:refs/tags/*

Please follow the instructions mentioned on the V8 wiki.