Currently we incorrectly show global object as arrow function receiver.
With this CL:
- if this is used inside of function we show correct this value,
- if this is unused and V8 optimizes it out - we show undefined.

Second is known issue which we should address separately.

R=dgozman@chromium.org,yangguo@chromium.org

Bug: chromium:552753
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Iac88a07fe622eb9b2f8af7ecbc4a32a56c8cdfaa
Reviewed-on: https://chromium-review.googlesource.com/723840
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48839}