Bug 843619: Remove tabs tray menu. [r=mfinkle] [needs-clobber]

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extra : rebase_source : 7f590f1f0b21e15ced7efd59f6cf0cf9394e4671
Bug 843619: Remove robocop test for tabs tray menu button. [r=gbrown]

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extra : rebase_source : 0eb9201646de0802290bd1ea2225325cb5a72fff