Mojo: Basic C++ wrappers for the (still-untested) data pipes.

I'd write tests, but I want to start from the "bottom up".

R=sky@chromium.org

Review URL: https://codereview.chromium.org/114813007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241419 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241419