Not so sure. I haven't worked on this code for a while and have no non-public knowledge of the bug, but ArrayBufferBuilder does not inherit from any of the GCed base classes, and has the USING_FAST_MALLOC macro which is used for non-GC classes. https://chromium.googlesource.com/chromium/src/+/refs/heads/...

The ArrayBuffer itself also uses reference counters rather than the GC base classes from Oilpan. https://chromium.googlesource.com/chromium/src/+/refs/heads/...

See also https://chromium.googlesource.com/chromium/src/+/refs/heads/... and https://chromium.googlesource.com/chromium/src/+/refs/heads/...