Kills some dead code because it is no longer possible to drag maximized windows. (https://codereview.chromium.org/80323002)

Also removes DragDetails::window_resizer which is no longer needed.

Review URL: https://codereview.chromium.org/144713003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247555 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247555