Currently, injected script source adds natural object properties before
internal properties. This can result in important ones such as
"[[PrimitiveValue]]" being left out. This CL
- makes sure internal properties are always added to preview
- removes unused "[[Iterator*]]" properties from preview
- boxed strings (e.g. new String("foo")) will not send unnecessary
properties 0:"f", 1:"o", 2:"o" if the [[PrimitiveValue]] is sent.

Bug: chromium:567265
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Icd5c7410351f371055277ce471226cc6fb5a861f
Reviewed-on: https://chromium-review.googlesource.com/634584Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Erik Luo <luoe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47622}