Port r24037 (d821bf9)

Original commit message:
These sentinels were in the wrong place, living in only tangentially related class TypeFeedbackInfo, but they codify state in the TypeFeedbackVector.

BUG=
R=dusan.milosavljevic@imgtec.com

Review URL: https://codereview.chromium.org/583573003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24046 ce2b1a6d-e550-0410-aec6-3dcde31c8c00