Revert of Make linux reference build 32-bit. We have some 32-bit bots still. (https://codereview.chromium.org/190723014/)

Reason for revert:
Breaks tough_media_cases benchmark.

BUG=351726

Original issue's description:
> Make linux reference build 32-bit. We have some 32-bit bots still.
> 
> BUG=347228
> TBR=matthewyuan@chromium.org
> NOTRY=True
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=256274

TBR=matthewyuan@chromium.org,cmp@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=347228

Review URL: https://codereview.chromium.org/196793008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256529 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256529