Bug 821000: Add "Mobile; " to the B2G desktop user agent, r=gerv, r=cjones

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extra : rebase_source : 4d0066f4fb8279c8dd78fee364bbb63828404df6
Bug 824199: Replace the marketplace-dev cert with the marketplace-prod test cert, r=rtilder

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extra : rebase_source : f2b9a1102e32c58a7d55ec4481b895af531d5e14
Bug 821207: Only allow signed apps to be installed from the Firefox Marketplace, and require all Firefox Marketplace apps to be signed, r=sicking

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extra : rebase_source : 746392a666bf23c43d309bf9546d2a4bb4d68f27
Bug 827499 - SettingsService: Fix locking problem. r=bent
Bug 823445 - Avoiding deadlocks and main-thread blockage on input streams, by not taking the lock in FileMediaResource::Close. r=roc, a=blocking-basecamp