- In an Else block it's possible to add more If<>'s in the same builder that are
  treated as an else if.
- Simplified and cleaned-up some of the IfBuilder's internals.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/66983002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17780 ce2b1a6d-e550-0410-aec6-3dcde31c8c00