[heap] Avoid scheduling tasks for callbacks during teardown

Instead run them synchronously.

Bug: chromium:890631
Change-Id: I3af68e335551d3754267ec0f51b895785ab7cd89
Reviewed-on: https://chromium-review.googlesource.com/1256925Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56341}

src/global-handles.cc

@@ -913,6 +913,7 @@ int GlobalHandles::PostGarbageCollectionProcessing(
   const int initial_post_gc_processing_count = ++post_gc_processing_count_;
   int freed_nodes = 0;
   bool synchronous_second_pass =
+      isolate_->heap()->IsTearingDown() ||
       (gc_callback_flags &
        (kGCCallbackFlagForced | kGCCallbackFlagCollectAllAvailableGarbage |
         kGCCallbackFlagSynchronousPhantomCallbackProcessing)) != 0;