[Examples] Move several simpler, single-purpose examples to extras to ensure Travis does not time out.

examples_extra/BackgroundPropertySetting/Sample/DemoCellNode.swift

@@ -0,0 +1,87 @@
+//
+//  DemoCellNode.swift
+//  BackgroundPropertySetting
+//
+//  Created by Adlai Holler on 2/17/16.
+//  Copyright © 2016 Adlai Holler. All rights reserved.
+//
+
+import UIKit
+import AsyncDisplayKit
+
+final class DemoCellNode: ASCellNode {
+	let childA = ASDisplayNode()
+	let childB = ASDisplayNode()
+	var state = State.Right
+
+	override init() {
+		super.init()
+		usesImplicitHierarchyManagement = true
+	}
+
+	override func layoutSpecThatFits(constrainedSize: ASSizeRange) -> ASLayoutSpec {
+		let specA = ASRatioLayoutSpec(ratio: 1, child: childA)
+		specA.flexBasis = ASRelativeDimensionMakeWithPoints(1)
+		specA.flexGrow = true
+		let specB = ASRatioLayoutSpec(ratio: 1, child: childB)
+		specB.flexBasis = ASRelativeDimensionMakeWithPoints(1)
+		specB.flexGrow = true
+		let children = state.isReverse ? [ specB, specA ] : [ specA, specB ]
+		let direction: ASStackLayoutDirection = state.isVertical ? .Vertical : .Horizontal
+		return ASStackLayoutSpec(direction: direction,
+			spacing: 20,
+			justifyContent: .SpaceAround,
+			alignItems: .Center,
+			children: children)
+	}
+
+	override func animateLayoutTransition(context: ASContextTransitioning!) {
+		childA.frame = context.initialFrameForNode(childA)
+		childB.frame = context.initialFrameForNode(childB)
+		let tinyDelay = drand48() / 10
+		UIView.animateWithDuration(0.5, delay: tinyDelay, usingSpringWithDamping: 0.9, initialSpringVelocity: 1.5, options: .BeginFromCurrentState, animations: { () -> Void in
+				self.childA.frame = context.finalFrameForNode(self.childA)
+				self.childB.frame = context.finalFrameForNode(self.childB)
+			}, completion: {
+				context.completeTransition($0)
+		})
+	}
+
+	enum State {
+		case Right
+		case Up
+		case Left
+		case Down
+
+		var isVertical: Bool {
+			switch self {
+			case .Up, .Down:
+				return true
+			default:
+				return false
+			}
+		}
+
+		var isReverse: Bool {
+			switch self {
+			case .Left, .Up:
+				return true
+			default:
+				return false
+			}
+		}
+
+		mutating func advance() {
+			switch self {
+			case .Right:
+				self = .Up
+			case .Up:
+				self = .Left
+			case .Left:
+				self = .Down
+			case .Down:
+				self = .Right
+			}
+		}
+	}
+}