Move OOMPriorityManager and LowMemoryObserver to chrome/browser/chromeos/.

BUG=none
TEST=none
Review URL: https://chromiumcodereview.appspot.com/10384098

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@136485 0039d316-1c4b-4281-b951-d872f2087c98
15 files changed