The final spec for Object.getPrototypeOf calls ToObject on the
parameter, which means that it should only throw for null and
undefined. For other non object values the prototype of the wrapper
should be used.

BUG=v8:3964
LOG=N
R=adamk, rossberg@chromium.org

Review URL: https://codereview.chromium.org/1014813003

Cr-Commit-Position: refs/heads/master@{#27354}