Uses the new Isolate version of methods.

Bug: v8:7754
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I1a38dd61d10899ae33ef796f4f443b11640315c2
Reviewed-on: https://chromium-review.googlesource.com/1143861
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54563}