Avoid reporting incorrect retaining paths in heap snapshots

The heap snapshot view in the dev tools reports a lot of incorrect
retaining paths involving weak references from FeedbackVectors. To fix,
when IndexedReferencesExtractor encounters a weak reference, it should
record a weak reference rather than a hidden reference. This way, the
forward reference is still visible when exploring in the summary view,
but weak references aren't reported as retainers.

Bug: v8:12112
Change-Id: Ib3bafc49482fb4f515877a90bae8707483d0a7a2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3101266Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#76364}

src/profiler/heap-snapshot-generator.cc

@@ -774,8 +774,13 @@ class IndexedReferencesExtractor : public ObjectVisitor {
       generator_->visited_fields_[field_index] = false;
     } else {
       HeapObject heap_object;
-      if (slot.load(cage_base).GetHeapObject(&heap_object)) {
+      auto loaded_value = slot.load(cage_base);
+      if (loaded_value.GetHeapObjectIfStrong(&heap_object)) {
         VisitHeapObjectImpl(heap_object, field_index);
+      } else if (loaded_value.GetHeapObjectIfWeak(&heap_object)) {
+        generator_->SetWeakReference(parent_, next_index_++, heap_object,
+                                     field_index * kTaggedSize);
+        generator_->visited_fields_[field_index] = false;
       }
     }
   }