Keep track of which maps are associated with prototype objects so we can tune the...

Keep track of which maps are associated with prototype objects so we can tune the fast-case vs. hash map heuristics accordingly.
This is a reland of r11681 https://chromiumcodereview.appspot.com/10448011 , which was reverted because of layout test failures that were actually caused by the long-standing issue fixed in https://chromiumcodereview.appspot.com/10515006 (r11706).
Review URL: https://chromiumcodereview.appspot.com/10532021

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11727 ce2b1a6d-e550-0410-aec6-3dcde31c8c00