Add repeat APIs to Tween

Summary:
Added API to Tween to allow animations to repeat

Fixes #116

Reviewers: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, featherless

Reviewed By: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, featherless

Subscribers: featherless

Tags: #material_motion

Differential Revision: http://codereview.cc/D3111

src/interactions/Tween.swift

@@ -32,6 +32,33 @@ public class Tween<T>: Interaction, Togglable, Stateful {
    */
   public let duration: ReactiveProperty<CGFloat>
 
+  /**
+   The number of times the animation will repeat.
+
+   If the repeatCount is 0, it is ignored. If both repeatDuration and repeatCount are specified the behavior is undefined.
+
+   Setting this property to greatestFiniteMagnitude will cause the animation to repeat forever.
+
+   See https://developer.apple.com/reference/quartzcore/camediatiming/1427666-repeatcount for more information.
+   */
+  public let repeatCount: ReactiveProperty<CGFloat> = createProperty("Tween.repeatCount", withInitialValue: 0)
+
+  /**
+   The number of seconds the animation will repeat for.
+
+   If the repeatDuration is 0, it is ignored. If both repeatDuration and repeatCount are specified the behavior is undefined.
+
+   See https://developer.apple.com/reference/quartzcore/camediatiming/1427643-repeatduration for more information.
+   */
+  public let repeatDuration: ReactiveProperty<CGFloat> = createProperty("Tween.repeatDuration", withInitialValue: 0)
+
+  /**
+   Will the animation play in the reverse upon completion.
+
+   See https://developer.apple.com/reference/quartzcore/camediatiming/1427645-autoreverses for more information.
+   */
+  public let autoreverses: ReactiveProperty<Bool> = createProperty("Tween.autoreverses", withInitialValue: false)
+
   /**
    The delay of the animation in seconds.
    */
@@ -137,6 +164,9 @@ public struct TweenShadow<T> {
   public let state: ReactiveProperty<MotionState>
   public let duration: ReactiveProperty<CGFloat>
   public let delay: ReactiveProperty<CGFloat>
+  public let repeatCount: ReactiveProperty<CGFloat>
+  public let repeatDuration: ReactiveProperty<CGFloat>
+  public let autoreverses: ReactiveProperty<Bool>
   public let values: ReactiveProperty<[T]>
   public let keyPositions: ReactiveProperty<[CGFloat]>
   public let timingFunctions: ReactiveProperty<[CAMediaTimingFunction]>
@@ -146,6 +176,9 @@ public struct TweenShadow<T> {
     self.enabled = tween.enabled
     self.state = tween._state
     self.duration = tween.duration
+    self.repeatCount = tween.repeatCount
+    self.repeatDuration = tween.repeatDuration
+    self.autoreverses = tween.autoreverses
     self.delay = tween.delay
     self.values = tween.values
     self.keyPositions = tween.keyPositions

src/systems/coreAnimationTweenToStream.swift

@@ -67,6 +67,9 @@ private func streamFromTween<T>(_ tween: TweenShadow<T>, configureEvent: @escapi
       }
       animation.beginTime = CFTimeInterval(tween.delay.value)
       animation.duration = CFTimeInterval(duration)
+      animation.repeatCount = Float(tween.repeatCount.value)
+      animation.repeatDuration = CFTimeInterval(tween.repeatDuration.value)
+      animation.autoreverses = tween.autoreverses.value
 
       let key = NSUUID().uuidString
       activeAnimations.insert(key)