Fix deprecated V8 function use in content_shell

Fixes use of deprecated Object::Set V8 function by instead using the
Context version and checking the return value.

Bug: v8:7283, v8:8562
Change-Id: Ia3ab123d36507576bde1a9dcd79ffbdc545469a4
Reviewed-on: https://chromium-review.googlesource.com/c/1454528
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Peter Beverloo <peter@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629162}
6 files changed