Revert "Prevent liveedit on or under generators with open activations"

Seems to crash some tests on buildbots.

TBR=ishell@chromium.org
CC=wingo@igalia.com,yangguo@chromium.org
BUG=

Review URL: https://codereview.chromium.org/273433002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21178 ce2b1a6d-e550-0410-aec6-3dcde31c8c00