Revert 244760 "Track when profiles are last used."

Speculatively reverted due to consistent linux asan failure for
StartupBrowserCreatorTest.ProfilesWithoutPagesNotLaunched.

http://build.chromium.org/p/chromium.memory/buildstatus?builder=Linux%20ASAN%20Tests%20%282%29&number=21744

> Track when profiles are last used.
> 
> This will allow use to ignore profiles unused for a certain length of time (likely 28 days) when calculating statistics on number of profiles, number of signed-in profiles, etc.
> 
> BUG=295817
> 
> Review URL: https://codereview.chromium.org/134863002

TBR=bcwhite@chromium.org

Review URL: https://codereview.chromium.org/136153005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244789 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244789