Apply numeric casts correctly in typed arrays and related code.

R=jkummerow@chromium.org
BUG=353004
LOG=Y

Committed: https://code.google.com/p/v8/source/detail?r=20020

Review URL: https://codereview.chromium.org/201873005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20022 ce2b1a6d-e550-0410-aec6-3dcde31c8c00