cppgc: Fix snapshot unittest

Bug: chromium:1056170
Change-Id: I84bc0f77ac4a27d310416bb00c4caf7fa3d76551
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2922104
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74815}

test/unittests/heap/unified-heap-snapshot-unittest.cc

@@ -361,8 +361,8 @@ TEST_F(UnifiedHeapSnapshotTest, MergedWrapperNode) {
   const size_t js_size = Utils::OpenHandle(*wrapper_object)->Size();
 #if CPPGC_SUPPORTS_OBJECT_NAMES
   const size_t cpp_size =
-      cppgc::internal::HeapObjectHeader::FromPayload(gc_w_js_ref.Get())
-          .GetSize();
+      cppgc::internal::HeapObjectHeader::FromObject(gc_w_js_ref.Get())
+          .AllocatedSize();
   ForEachEntryWithName(snapshot, GetExpectedName<GCedWithJSRef>(),
                        [cpp_size, js_size](const HeapEntry& entry) {
                          EXPECT_EQ(cpp_size + js_size, entry.self_size());