Now that we have the PlainPrimitiveToNumber operator(s), we can unify
all the places where we expect a number, but can also safely handle any
plain-primitive (via ToNumber truncation).

Drive-by-fix: Also handle Math.min consistently with Math.max.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2064953004
Cr-Commit-Position: refs/heads/master@{#36984}