Pipe through Isolate into several elements.cc functions, to avoid using
HeapObject::GetIsolate. In some cases, uses ReadOnlyObject::GetIsolate
which is allowed.

(Autogenerated using Leszek's clang-bubble-getisolate)

Bug: v8:7786
Change-Id: Idcbfaadf95c3c2b96d03b606da5594774bac2f7e
Reviewed-on: https://chromium-review.googlesource.com/1107706Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53932}