Use Unique<Map> in HTransitionElementsKind.

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/23693006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16864 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use Unique<Cell> and Unique<PropertyCell> in LoadGlobalCell and StoreGlobalCell.

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/24072016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16865 ce2b1a6d-e550-0410-aec6-3dcde31c8c00