sync: move ProfileSyncService early-init code from StartUp to Initialize

Since this means doing a bit more work in Initialize that will need tear
down at destruction time, move some tear-down code to Shutdown and call
it from the destructor.

This is in preparation for an upcoming change to move
slow-startup control of PSS into a separate class.

BUG=80194

Review URL: https://codereview.chromium.org/153893008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250561 0039d316-1c4b-4281-b951-d872f2087c98
Revert 250320 "Make the libc overrides in zygote_main_linux.cc s..."

> Make the libc overrides in zygote_main_linux.cc sanitizer-friendly.
> 
> Previosly they would bypass sanitizer interceptors and call the libc
> implementations directly. No bueno.
> 
> BUG=123263
> R=jln@chromium.org
> 
> Review URL: https://codereview.chromium.org/158833004

TBR=earthdok@chromium.org

Review URL: https://codereview.chromium.org/159393003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250563 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250563