Fix and improve Map::CurrentMapForDeprecatedInternal().

Inline relevant bits from Map::FindUpdatedMap() and Map::IsMoreGeneralThan()
into Map::CurrentMapForDeprecatedInternal() to fix issues introduced
with field type tracking, avoid the useless second pass over the transition
tree, and finally make it easier to understand what this method actually
does.

TEST=mjsunit/regress/regress-365172-2
R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=20997

Review URL: https://codereview.chromium.org/257893004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21010 ce2b1a6d-e550-0410-aec6-3dcde31c8c00