Move some non-event related functionality from RootWindow onto RootWindowHost.

- Transform logic
- Compositor

R=sky@chromium.org
http://crbug.com/308843

Review URL: https://codereview.chromium.org/70103020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236017 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236017