Mark/IsIndependent is marked V8_DEPRECATE_SOON, but is still needed in some
places. In order to allow us to warn on V8_DEPRECATE_SOON within V8, explicity
disable deprecation warnings on these calls temporarily.

BUG=v8:7754

Change-Id: I0a7f3aedc04412c120217ba83d2cf91aafff568d
Reviewed-on: https://chromium-review.googlesource.com/1147751
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54670}