Only update POLYMORPHIC stubs using other POLYMORPHIC or GENERIC stubs.

Review URL: https://chromiumcodereview.appspot.com/12088021

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13530 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Improved printing of jump tables.

Review URL: https://codereview.chromium.org/12093016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13531 ce2b1a6d-e550-0410-aec6-3dcde31c8c00