This uses the type feedback already present for computed value stores
into object literals to generate optimized stores in Crankshaft, thus
avoiding unnecessary generic stores with side effects.

R=svenpanne@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9692036

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11023 ce2b1a6d-e550-0410-aec6-3dcde31c8c00