Layer backed nodes thrash issue

[wsdwsd0829]

Layer backed nodes will get following calls very often (thrashing) during UIKit operations like reloadItemAtIndexPath: or pop a view top view controller will be thrashed!!!):

- (id<CAAction>)actionForLayer:(CALayer *)layer forKey:(NSString *)event
{
  if (event == kCAOnOrderIn) {
    NSLog(@"&&&& entering: %@", self);
    [self __enterHierarchy];
  } else if (event == kCAOnOrderOut) {
    NSLog(@"&&&& exiting: %@", self);
    [self __exitHierarchy];
  }
  ASDisplayNodeAssert(_flags.layerBacked, @"We shouldn't get called back here unless we are layer-backed.");
  return (id)kCFNull;
}

Problems

• Problem 1: Even though interface coalescing will solve didEnterVisible calls correctly for views, it will not for isLayerBacked nodes.
• Problem 2: __exitHierarchy will [self._locked_asyncLayer cancelAsyncDisplay]; causing some layerBacked view’s not updated properly during thrashing.

Solutions

• Sol for 1; during “exiting”, layer will exit visible interface state no matter what, we should update their interface state when entering hierarchy. Since rangedMangedNodes will enter top down, a non-layerbacked ancestor’s pendingInterfaceState seems to be reasonable candidate.
• Sol for 2: Do not cancel display for layerBackedNodes because they must be descendant of some view backed nodes which will be cancelled correctly as before.

[ghost]

	1 Warning
⚠️	Any source code changes should have an entry in CHANGELOG.md or have #trivial in their title.

Generated by 🚫 Danger

[wsdwsd0829]

The fix is not ideal, may better just remove [self._locked_asyncLayer cancelAsyncDisplay];? (it seems to used before interface state is introduced)

[wsdwsd0829]

Will fix them separately with better approaches.