Runtime assert added to %NormalizeElements.
Runtime assert added to %NormalizeElements.

BUG=399654
LOG=N
R=danno@chromium.org

Review URL: https://codereview.chromium.org/423073007

git-svn-id: f98b9d40cb02301bc76fa9e1b46ee668158567fd@22809 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh