Bug 1083895 - favicon should not change if link element isn't in DOM, r=bz

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extra : rebase_source : 6d8c8e5ecab8021fa5d42ba4b6fc82a7315fcc79
Bug 1079707 - asyncresolve can throw, r=alexbardas

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extra : rebase_source : e1a83fed31780d9e1d56dc795e157e17525ff9f6