Port r11817 (616dfcf0)

Original commit message:
Each SharedFunctionInfo gets an optimized code map to store
one optimized code object per context. When allocating a new
closure we consult this map and check if there is optimized code
that can be shared.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10557002
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11848 ce2b1a6d-e550-0410-aec6-3dcde31c8c00