We use LoadFromPrototype also for direct global loads. InitPrototypeChecks did not support this though, and would create a prototype chain check for objects beyond the direct global. This tries to ensure the property on the global itself doesn't exist, which is invalid.

Additionally this CL deletes duplicate code.

BUG=chromium:702798,v8:5561

Change-Id: I318a5b6cd5f7c3efdb3a003e34edd37d5d3f880b
Reviewed-on: https://chromium-review.googlesource.com/457369
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43935}