This is needed so that we can start removing write-barriers in optimized
code if we can prove that the receiver object is always in new-space.

TEST=cctest/test-heap/OptimizedAllocationAlwaysInNewSpace

Review URL: https://chromiumcodereview.appspot.com/10008007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11243 ce2b1a6d-e550-0410-aec6-3dcde31c8c00