Make delete command not to remove elements with non-static CSS position

Starting r8935(http://trac.webkit.org/changeset/8935), delete command removes elements with non-static CSS position property, e.g. relative, before/after selection to delete or such elements to be empty after deleting.

This behavior makes users confusing due by remove unexpected elements are removed as described in issue 272181.

This patch changes delete command behavior not to remove elements with non-static CSS position property before selection to delete.

BUG=272181
TEST=LayoutTests/editing/deleting/delete-non-static-position.html
R=ojan@chromium.org

Review URL: https://codereview.chromium.org/22903006

git-svn-id: svn://svn.chromium.org/blink/trunk@156803 bbb929c8-8fbe-4397-9dbb-9b2b20218538