Move auto layout code to WindowPositioner
* remove auto_window_management.{h|cc}
* remove GetTopWindowForNewWindow

BUG=272460

Review URL: https://codereview.chromium.org/26899004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228108 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228108