Backout 119105935766 for crash during test_install_receipts.xul.
Bug 827961: Add explicit parens around condition in nsHTMLMediaElement::UpdateAudioChannelPlayingState(), to fix build warning (treated as error in warnings-as-errors builds). r=roc
  Bug 827503 - use nsMainThreadPtrHolders when passing XPCWrappedJSes around off main thread, r=bholley,jst a=blocking-basecamp+