Revert 99391 (broke CrOS unit_tests) - Set user-visible machine names and devices types for synce...

Revert 99391 (broke CrOS unit_tests) - Set user-visible machine names and devices types for synced sessions.

On OSX:
- Read the computer name, falling back to reading hw.model and stripping any trialing numbers. This will give us
  something like MacBookPro, iMac, MacBookAir.
On Linux:
- Use distro name which gives something like "Ubuntu 10.04.2 LTS".
On Windows:
- Use the computer name
On ChromeOS:
- Use "Chromebook"

BUG=94693, 59672
TEST=enable session sync, sync two clients, and then look at the entries in about:sync and see that the "client_name" is set

Review URL: http://codereview.chromium.org/7740055
Patch from Yaar Friedman <yfriedman@chromium.org>;.

TBR=thakis@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=99394