The change in r4990 contained a bug in Math.pow. One of the arguments for the call to runtime where clobbered if allocation of the heap number for the result failed.

Caught by a couple of Mozilla tests which does a lot of calls to Math.pow.

Fix presubmit error in x64.
Review URL: http://codereview.chromium.org/2847037

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4993 ce2b1a6d-e550-0410-aec6-3dcde31c8c00