Bug 1114989 - Mark Shmem::mSegment as non-owning

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extra : rebase_source : c37e0768470315fd3dadeeeb3343b64f93a83b40
Bug 1114880 follow-up: Rename MOZ_{STRONG,WEAK}_REF to MOZ_{OWNING,NON_OWNING}_REF

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extra : rebase_source : 51fff0785d112b5b87be3c6ff723c8986b37effe