heap-snapshot-generator: Get copy of edge name

Edge names are not always string constants and have to be deleted at
some point. Copy them over to StringStorage to allow the embedder
freeing up their copy.

Bug: chromium:936797
Change-Id: I1c1a617c79c2016b3bd30c3460bb7a47edce1b95
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1565903
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60849}

src/profiler/heap-snapshot-generator.cc

@@ -1932,7 +1932,8 @@ bool NativeObjectsExplorer::IterateAndExtractReferences(
       if (edge.name == nullptr) {
         from->SetIndexedAutoIndexReference(HeapGraphEdge::kElement, to);
       } else {
-        from->SetNamedReference(HeapGraphEdge::kInternal, edge.name, to);
+        from->SetNamedReference(HeapGraphEdge::kInternal,
+                                names_->GetCopy(edge.name), to);
       }
     }
   }