Bug 942432 - Remove nsIJSEventListener::mContext, r=bz

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extra : rebase_source : 0339018010bd6a079080f603db231837bfa9bf00
Bug 943613 - Notify JS implemented Event Target when an event listener is added / removed, r=bz

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extra : rebase_source : 88de22115dfef896468f2bb91d60f880cd84cfd3
Bug 937763 - Don't emit MIR marked as emittedAtUses immediately when redefining. (r=jandem)