Summary:
@public
Limit child cloning to layout calculation. This also allows for mixing shared and owned children.
Rationale:
We do allow for shared children if the caller manages themselves. The single known use case is React Native.
So far, we have cloned children eagerly whenever child lists are mutated, or layout is run. This was to allow for a quick check of the owner of any first child, assuming that either *all* or *no* child of a node are shared.
For Yoga/Java, we want to get rid of global weak JNI refs, and these are also used to invoke clone callbacks. We can achieve that goal by switching to an alternative approach, passing additional data to the layout pass. This additional data has to be passed to any configured cloning callback. Therefore, it is desirable to **only call cloning functions during the layout pass.**
The obvious solution seems to be to not uphold the invariant of the first child determining shared/owned state of all siblings, and allow for a mix of shared and own children.
Reviewed By: shergin
Differential Revision: D14136223
fbshipit-source-id: 34490cfeeb2170c99d6ed1b9bdcbcedb316813af
b1c749075d