`MatrixMessage` is [serialized](https://searchfox.org/mozilla-central/rev/278046367dab878316f60f0bd7f740cf73f3c447/gfx/layers/ipc/LayersMessageUtils.h#75) using a `PlainOldDataSerializer` but it contains a `mozilla::Maybe` which I don't think is POD. At least, it has its own serialization code [here](https://searchfox.org/mozilla-central/rev/278046367dab878316f60f0bd7f740cf73f3c447/ipc/glue/IPCMessageUtils.h#1051). So we probably shouldn't be using PlainOldDataSerialize for `MatrixMessage`.
Bug 1620719 Comment 2 Edit History
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`MatrixMessage` is [serialized](https://searchfox.org/mozilla-central/rev/278046367dab878316f60f0bd7f740cf73f3c447/gfx/layers/ipc/LayersMessageUtils.h#75) using a `PlainOldDataSerializer` but it contains a `mozilla::Maybe` which I don't think is POD. At least, it has its own serialization code [here](https://searchfox.org/mozilla-central/rev/278046367dab878316f60f0bd7f740cf73f3c447/ipc/glue/IPCMessageUtils.h#1051). So we probably shouldn't be using `PlainOldDataSerializer` for `MatrixMessage`.