This removes explicit uses of the RUNTIME_ASSERT macro from some runtime
methods. The implicit ones in CONVERT_FOO_ARG_CHECKED will be addressed
in a separate CL for all runtime modules at once.

R=titzer@chromium.org
BUG=v8:5066

Review-Url: https://codereview.chromium.org/2125793002
Cr-Commit-Position: refs/heads/master@{#37547}