Handlify JSObject::DeepCopy method.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/22934006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16708 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use regular map-checks to guard string-length loading.

R=ulan@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23702039

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16709 ce2b1a6d-e550-0410-aec6-3dcde31c8c00