deps: cherry-pick 50f7455 from upstream V8

Original commit message:

    [inspector] added Runtime.globalLexicalScopeNames method

    The method returns names for all available top-level scope variables
    in giving context.

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

    Bug: chromium:681333
    Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
    Change-Id: I2d0b600e1afbfef9087f53ea9c26abe1e112047c
    Reviewed-on: https://chromium-review.googlesource.com/719409


    Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#48618}

Refs: https://github.com/v8/v8/commit/50f7455cd973864fe70cc04f97146f725b7c3e54

PR-URL: https://github.com/nodejs/node/pull/16591


Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>