Verify that no-side-effects scope does not add unsafe phis and does not change push-pop balance of the environment.

R=danno@chromium.org
BUG=v8:2671

Review URL: https://chromiumcodereview.appspot.com/14696015

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14610 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use AssumeRepresentation when the representation is known and will not change.

R=danno@chromium.org

Review URL: https://chromiumcodereview.appspot.com/14793014

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14611 ce2b1a6d-e550-0410-aec6-3dcde31c8c00