Linux
is a basic UNIX-like kernel. The various Linux distros come with assorted WMs and applications and so forth, but Linux is just the kernel.
That's why Richard Stallman keeps on ranting that people should call it GNU/Linux, as all the stuff other than the kernel is basically taken from his
GNU project, or other stuff released under the GNU Public License or licenses deemed to be compatible (or at least not incompatible) with it.
From the GNU homepage:
"GNU's kernel isn't finished, so GNU is used with the kernel Linux. The combination of GNU and Linux is the GNU/Linux operating system, now used by millions.
"Sometimes this combination is incorrectly called Linux. There are many variants or 'distributions' of GNU/Linux."
So it looks like Google are doing exactly what you describe