DebugEvaluate contains code since 2009 that bypasses JSGlobalProxy and
returns JSGlobalObject when result of expression is global proxy.
This behavior may be dangerous:
- JSGlobalObject does not perform security checks,
- some parts of V8 code do not ready for JSGlobalObject, e.g.,
  SetHashAndUpdateProperties function will crash on DCHECK if we will
  try to store JSGlobalObject to map.

At the same time it looks like there is no any valid use case for it.

R=yangguo@chromium.org

Bug: none
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ib0e35d5ae9ef47318c866e44c5c6856e34ed05a5
Reviewed-on: https://chromium-review.googlesource.com/1198764Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55550}