Rename ReverseCondition to CommuteCondition, a more standard term.

R=dcarney@chromium.org, dcarney
BUG=

Review URL: https://codereview.chromium.org/313083006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21677 ce2b1a6d-e550-0410-aec6-3dcde31c8c00