Some cleanup and a small bug in the WorkspaceLayoutManager

BUG=-
TEST=-

Review URL: https://codereview.chromium.org/188743003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255461 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255461