Massive cleanup and refactoring, and also enable linking to a specific version of an SDK.

The real changes are everything outside of the "out" directory. I updated the
compiled version of the out directory, because the current plain checkout
doesn't run out-of-the-box.

Please see actual review at: https://codereview.chromium.org//297293008

BUG=

Review URL: https://codereview.chromium.org//298333006