Only flush SharedFunctionInfo optimized code cache when necessary

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/14604007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14650 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge commit 'd045fbd308cf786fdf6fdcf5cfd9f1a0894f33b9' into hj-dev-palfia
MIPS: Only flush SharedFunctionInfo optimized code cache when necessary

Port r14650 (d045fbd3)