Support merging with distinct attributes.

R=danno@chromium.org

Review URL: https://chromiumcodereview.appspot.com/14756012

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14595 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix environment in HOptimizedGraphBuilder::VisitCountOperation. Follow-up for r14584.

R=danno@chromium.org
BUG=v8:2671
TEST=mjsunit/regress/regress-2671-1.js

Review URL: https://chromiumcodereview.appspot.com/14972009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14596 ce2b1a6d-e550-0410-aec6-3dcde31c8c00