These methods now return undefined upon finding a data property in the
prototype chain which shadows an accessor property, and when hitting
a Proxy, call the appropriate proxy traps.

R=cbruni@chromium.org, littledan@chromium.org
BUG=v8:5130

Review-Url: https://codereview.chromium.org/2592013003
Cr-Commit-Position: refs/heads/master@{#41929}