* Revert "Revert "[ASLayoutSpec] Use childrenMap directly to prevent creating an NSArray within ASDK (#1937)""
This reverts commit 735b4ebd0872483044d98a5d05b43324e76fc8d4.
* Fix crash and add exception for mutating while using fast enumeration of ASLayoutSpec children
NSFastEnumeration is potentially quite dangerous in the wrong hands. In particular, it does not provide a safe mechanism for you to return temporary objects directly, and it does not provide any guarantee that you will be called when the enumeration has completed; therefore if we generate temporaries and store them in an instance variable, we will not necessarily be able to clean them up! This means fast enumeration methods should never be called within an autorelease pool or the autorelease pool be drained within the fast enumeration loop.
The reason is we store references to objects in the stackBuf struct by casting the child pointer to __autoreleasing id. If we pop the autorelease pool between calls to -countByEnumeratingWithState:objects:count:, it will die in a messy explosion of pointer dereferences and EXC_BAD_ACCESS.
* Add tests for ASDisplayNode and ASLayoutSpec fast enumeration
- -layoutSpecThatFits: must return an ASLayoutSpec.
- Move ASDisplayNode's -measureWithSizeRange: redeclaration to ASDisplayNode.h.
- Rename ASStackLayoutChild.h to ASStackLayoutDefines.h.
- Rename ASStaticLayoutSpecDimension.h to ASRelativeSize.h.
- Don't import ASLayout.h in other headers to prevent circular inclusions.
- Explain use cases of ASLayout's initializers.
- Clean up ASInternalHelpers.h.
- constrainedSizeForCalculatedLayout is of type ASSizeRange.
- calculatedLayout is better explained.
- Since ASLayout is cached and reused, its position property is mutable.
