Bug 889120 - Australis' customize tab gets mixed up with other tab, r=jaws

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extra : rebase_source : 12ef7ad03ece347dccd1e193a24e4e74b7b20b82
Bug 932947 - Make the styling of Australis' customizable dragged items look more like Philipp's prototype.  r=Gijs, ui-r=phlsa

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extra : rebase_source : b0b0c41294844266a06f0a74dc168c2224c5230f