Bug 968825 - Null pointer checks in LayerTransactionParent - r=jrmuizel
Bug 970747 - 1/6 - Make ContainerLayer::InsertAfter always perform checks and return bool - r=mattwoodrow
Bug 970747 - 2/6 - Make LayerTransactionParent::RecvUpdate error out if InsertAfter fails - r=mattwoodrow
Bug 970747 - 3/6 - Make ContainerLayer::RemoveChild always perform checks and return bool - r=mattwoodrow
Bug 970747 - 4/6 - Make LayerTransactionParent::RecvUpdate error out if RemoveChild fails - r=mattwoodrow
Bug 970747 - 5/6 - Make ContainerLayer::RepositionChild always perform checks and return bool - r=mattwoodrow
Bug 970747 - 6/6 - Make LayerTransactionParent::RecvUpdate error out if RepositionChild fails - r=mattwoodrow