In ES6 Object.getOwnPropertyDescriptor should call ToObject, which
means that primitive values will return descriptors from the wrapper.

BUG=v8:3964
LOG=N
R=adamk, rossberg@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/998163004

Cr-Commit-Position: refs/heads/master@{#27569}