Instead of allocating fresh temporary lists for every instruction, reuse
the same instance and reset it between instructions.

This reduces the amount of zone memory used for inserting the HChange
instructions roughly by half.

Review URL: http://codereview.chromium.org/6628079

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7094 ce2b1a6d-e550-0410-aec6-3dcde31c8c00