MIPS: Share optimized code for closures.

MIPS: Share optimized code for closures.

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=

Committed: https://code.google.com/p/v8/source/detail?r=11848

[Michael Starzinger, 2012-06-18 12:41:38]

LGTM (with one comment). But still landing and addressing comment in a separate
CL.

https://chromiumcodereview.appspot.com/10557002/diff/1/src/mips/code-stubs-mi...
File src/mips/code-stubs-mips.cc (right):

https://chromiumcodereview.appspot.com/10557002/diff/1/src/mips/code-stubs-mi...
src/mips/code-stubs-mips.cc:162: __ Branch(&install_unoptimized);
It seems that this branch unconditionally installs the unoptimized code if the
first entry in the table doesn't match. This bug is also present on ARM and
seemed to have slipped my review of the original CL. I'll fix that in a separate
CL for both architectures after landing this.