The destructor of the owner of a phantom handle must clear the phantom
handle first before calling any function that can trigger GC.

Bug: chromium:827806
Change-Id: I20141d0d710c486aec3d92e729d76a53069e16fd
Reviewed-on: https://chromium-review.googlesource.com/992093Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52325}