MIPS: Avoid handle dereference during graph optimization.

Port r13475 (0076e1ee)

Original commit message:
With parallel recompilation enabled, objects made accessible by handles may
have changed between graph construction and graph optimization. Therefore
we must not assume that information on those objects remain the same between
those two phases. To police this, we forbid handle dereferencing during
graph optimization.
Exceptions to this rule are:
 - Dereferencing the handle to obtain the raw location of the object. This
   is safe since parallel recompilation acquires RelocationLock
 - Some places that dereference the handle for a type check. These are checked
   to be safe on a case-by-case basis.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/12049037
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13477 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Move polymorphic stub computation and compilation to stub cache

Review URL: https://chromiumcodereview.appspot.com/11953025

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13478 ce2b1a6d-e550-0410-aec6-3dcde31c8c00