Partial revert of "Next bunch of fixes for check elimination".

Partial revert of "Next bunch of fixes for check elimination".

This reverts the part of r21154 that introduced the CHECK()s to verify
state of objects with stable maps during code generation. The CHECK()s
seem to trigger a non-critical hidden bug in the map stability
mechanism. We will re-add these CHECK()s once the bug is found and
fixed.

BUG=372173
LOG=y
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/287363002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21352 ce2b1a6d-e550-0410-aec6-3dcde31c8c00