Revert 183501
Revert 183501

Per discussion on chrome-infrastructure-team,
this CL did not go through proper review channels
and needs more testing before being deployed on
main waterfall.

> Migrate master.chromium bots to Ubuntu Precise.
> 
> BUG=170262
> Review URL: https://codereview.chromium.org/12313007

TBR=phajdan.jr@chromium.org
Review URL: https://codereview.chromium.org/12315050

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@184044 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build