ASVideoNode should play when its player is ready and if it is expected to play (#2876)

- When a video node is first visible, it's player is called to play if auto play flag is on. However, the player might not be ready by that time, especially when the video is loaded on a slow network. The player just continues loading its asset.
- When the player is ready, we should check if it is expected to be playing and if true, try to play again.

Author: nguyenhuy

AsyncDisplayKit/ASVideoNode.mm

@@ -314,6 +314,9 @@ - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(N
       if ([change[NSKeyValueChangeNewKey] integerValue] == AVPlayerItemStatusReadyToPlay) {
         if (self.playerState != ASVideoNodePlayerStatePlaying) {
           self.playerState = ASVideoNodePlayerStateReadyToPlay;
+          if (_shouldBePlaying && ASInterfaceStateIncludesVisible(self.interfaceState)) {
+            [self play];
+          }
         }
         // If we don't yet have a placeholder image update it now that we should have data available for it
         if (self.image == nil && self.URL == nil) {