Revert 255982 "Enable App List Sync by default"

breaks unit_tests: http://build.chromium.org/p/chromium.linux/builders/Linux%20GTK%20Tests/builds/799

> Enable App List Sync by default
> 
> BUG=305024
> For chrome/browser/sync
> 
> R=jennyz@chromium.org, tapted@chromium.org
> TBR=zea@chromium.org
> 
> Review URL: https://codereview.chromium.org/187813006

TBR=stevenjb@chromium.org

Review URL: https://codereview.chromium.org/190533017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256021 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256021