X87: Reland 21774: Generate KeyedLoadGeneric with Hydrogen

Port r21781 (4869c528)

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/336543002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21813 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Rewrite GetPropertyAttribute to use the LookupIterator

BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/321543004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21814 ce2b1a6d-e550-0410-aec6-3dcde31c8c00