Contributing
Review the Building page.
We have a number of buildbots running continuous testing of our code. You can take a look and see if the commit you are basing your work on is solid. You can also follow the state of your work when we take your pull request.
Before we can use your code, you must sign the Google Individual Contributor License Agreement (CLA), which you can do online. The CLA is necessary mainly because you own the copyright to your changes, even after your contribution becomes part of our codebase, so we need your permission to use and distribute your code. We also need to be sure of various other things—for instance that you'll tell us if you know that your code infringes on other people's patents. You don't have to sign the CLA until after you've submitted your code for review and a member has approved it, but you must do it before we can put your code into our codebase.
Fork our repository, and start sending us pull requests.