Use Unique<Map> in CompareMap.

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/24243005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16843 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Handlify JSReceiver::SetPropertyWithDefinedSetter method.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/24176002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16844 ce2b1a6d-e550-0410-aec6-3dcde31c8c00