Fix Object.freeze, Object.observe wrt CountOperation and CompoundAssignment.

BUG=2774,2779
R=adamk@chromium.org

Review URL: https://chromiumcodereview.appspot.com/22562004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16111 ce2b1a6d-e550-0410-aec6-3dcde31c8c00