As part of J2V8 development (https://github.com/eclipsesource/J2V8),
we realized that we had a subtle bug in how Isolate scope was created
and it's lifetime managed, see:
https://github.com/eclipsesource/J2V8/issues/313.

Mentioned above bug was fixed, however, what we also noticed is that
V8 API has been constantly and slowly moving to such an API, in which
one has to pass Isolate explicitly to methods and/or constructors. We
found two more places that might have been overlooked. This contribution
adds passing of Isolate pointer explicitly to constructors of
String::Utf8Value and String::Value classes.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng;master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I61984285f152aba5ca922100cf3df913a9cb2cea
Reviewed-on: https://chromium-review.googlesource.com/593309
Commit-Queue: Adam Klein <adamk@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47656}