PromiseHooks can be called with a proxy which fails the cast and
crashes. This patch changes the runtime functions to
explicitly check for a JSPromise.

This has the side effect of removing the existing broken support for
catch prediction for non native promises.

Bug: v8:7398, v8:7190
Change-Id: I66dbe5f9935943a91afb7ee14919bd9248f9f7e4
Reviewed-on: https://chromium-review.googlesource.com/907677Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51182}