Clipboard synchronization between Chromium OS and guest OS

Here is my attempt at solving the clipboard synchronization problem:
*   I created a simple Chromium OS application. It listens on TCP port 30001: If the input from the connection starts with a P, it copy the rest of the data in the clipboard; If not, it outputs the content of the clipboard. It uses a dirty trick to update the clipboard (copy the text in a textarea, select it, then call the copy or paste command): I looked around, and it seems like it's the only way to do it...
*   On the guest OS, xclip is used to fetch and update the clipboard content.
*   ratpoison contains a new hook, that calls a script called croutonclip. That script figures out the current and next window, and copies the clipboard content as necessary.

There are still a few FIXME in the code. In particular, I am concerned about the dependency on netcat.

I'm not sure how easy it is to review the code with github, since this branch contains a number of incremental commits. If you want I can squash them in logical units.