Bug 827188 - Initialize the hidden private window lazily; r=bzbarsky

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extra : rebase_source : 42a4a4da52f0eaa57a83dc4daf0e1a47401f4411
Bug 827023 r=vingtetun
Bug 827772 - Followup to the patch in Bug 824695 r=jst
Backed out changeset f3a6aff3dbbc (bug 827188) because of build failures

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extra : rebase_source : 87d6ba184e23dbe83a3a0e2ae83c44c5ecdb46db
Bug 827188 - Initialize the hidden private window lazily; r=bzbarsky
Bug 821012 - B2G emulator install_gecko step should use busybox if available, r=jgriffin
Bug 827359 - Disable unconditional use of NEON code in WebRTC DSP code. r=jesup
Bug 826606 - Set uninitialized values for DeviceProximityEvent according to spec. r=dougt,smaug,khuey