Only splits into separate files, no other changes.

Change-Id: Icc0da2c5f18e03e9ed7c0043bd7c790f741900f2
Reviewed-on: https://go-review.googlesource.com/21804Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>