[Weakrefs] Fix incorrect check about previous/next weakref

When iterating over the holdings inside the cleanup callback,
we could potentially unregister the weakref which is next or
prev on the key list causing these checks to be incorrect.

Bug: v8:9360, v8:8179
Change-Id: I53ea12346eb4882b16a82677b64ba2c756d23a1c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1658161Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62165}

src/diagnostics/objects-debug.cc

@@ -1278,14 +1278,8 @@ void WeakCell::WeakCellVerify(Isolate* isolate) {
                 key_list_next().IsUndefined(isolate));
 
   CHECK(key_list_prev().IsWeakCell() || key_list_prev().IsUndefined(isolate));
-  if (key_list_prev().IsWeakCell()) {
-    CHECK_EQ(WeakCell::cast(key_list_prev()).key_list_next(), *this);
-  }
 
   CHECK(key_list_next().IsWeakCell() || key_list_next().IsUndefined(isolate));
-  if (key_list_next().IsWeakCell()) {
-    CHECK_EQ(WeakCell::cast(key_list_next()).key_list_prev(), *this);
-  }
 
   CHECK(finalization_group().IsUndefined(isolate) ||
         finalization_group().IsJSFinalizationGroup());

test/mjsunit/mjsunit.status

@@ -242,8 +242,6 @@
   # BUG(v8:9260)
   'tools/profviz': [SKIP],
 
-  # BUG(v8:9360)
-  'harmony/weakrefs/unregister-inside-cleanup5': [SKIP],
 }],  # ALWAYS
 
 ['novfp3 == True', {