This changes the last few remaining RUNTIME_ASSERT calls that need to be
intentionally robust because fuzzers or other callers can invoke the
runtime functions in question with unsafe arguments.

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

Review-Url: https://codereview.chromium.org/2122173003
Cr-Commit-Position: refs/heads/master@{#37576}