Undock window if a window is maximized while being dragged

BUG=338235
TEST=DockedWindowResizerTest.MaximizedDuringDrag

Review URL: https://codereview.chromium.org/148063003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249042 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249042