Revert 226921 "Don't pull in content_switches.cc to whole chrome..."

Likely increased mac binary size by 36 MB (crbug.com/304153)

> Don't pull in content_switches.cc to whole chrome code base
> 
> The point of this change is remove compilation of content_switches.cc
> that was done in installer_util target. This is a static library
> that other parts of chrome pull in and that makes the Chrome code that
> references those switches compile even if the switches itself are
> not exported.
> Installer_util doesn't even seem to uses those switches AFAIK.
> 
> Dropped compilation of these files so these problems are actually
> exposed and addressed by the person adding the switch. The main
> offender that referenced those switches was chrome's about_flags.cc.
> 
> BUG=
> 
> Review URL: https://codereview.chromium.org/24994002

TBR=rchlodnicki@opera.com

Review URL: https://codereview.chromium.org/26006005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227028 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227028