Bug 921178 - Remove unused fallback marking bitmap; r=billm

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extra : rebase_source : 4b53c8eb16d332ad8916a0abf4dd6ccd5f211ed4
Bug 921140 - Do not force an allocation for typical zone vectors; r=billm

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extra : rebase_source : 3b2b664643d2123c558a7fcce8f6248fd35dec7c
Bug 609896 - Optimize copy and initialization of DenseElements; r=billm

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extra : rebase_source : a0cf2605a7f1277352ff9163379632992c56d09a