The idea behind this commit is that handles_sp and leaf are two
concepts that are not mutually independent.  By making one explicitly
depend another, we can reduces the number of lines of codes written,
thus making things concise.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65426 b2dd03c8-39d4-4d8f-98ff-823fe69b080e