This is a refactoring-only CL and the third one in a series for enabling
inlining of accessors. The goal of this CL is to move the builders for accessors
to the places where we might be able to inline them later, i.e. the VisitFoo and
HandleBar member functions of HGraphBuilder.
Extracted duplicate code into LookupAccessorPair.
Review URL: https://chromiumcodereview.appspot.com/10831047
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12209 ce2b1a6d-e550-0410-aec6-3dcde31c8c00