Support transforms forming containing blocks (#1539)

Summary:
X-link: https://github.com/facebook/react-native/pull/42191

Pull Request resolved: https://github.com/facebook/yoga/pull/1539

React native supports transforms and if a node has a transform it will [form a containing block for absolute descendants regardless of position type](https://developer.mozilla.org/en-US/docs/Web/CSS/Containing_block#identifying_the_containing_block). So we need to pass that information into Yoga to ensure this happens.

The verbiage for the field "alwaysFormsContainingBlock" is very specific. In a vacuum a node cannot simply "form a containing block". It only forms a containing block in reference to a different node. This can be illustrated in a scenario where we have a static node that is a flex container which has 1 absolute child and 1 relative child. This static node will form a containing block for the relative child but not the absolute one. We could just pass the information on rather something has a transform or not but Yoga is not supposed to know about transforms in general. As a result we have a notion of "always" forming a containing block. Since Yoga is a flexbox spec, non-absolute nodes' containing blocks will ways be their parent. If we add something like a transform to a node then that will also apply to absolute nodes - hence we can say the node will **always** form a CB, no matter who is the descendant.

Changelog: [Internal]

Reviewed By: NickGerleman

Differential Revision: D52521160

fbshipit-source-id: bab9319ffddec617f5281823930f2a00cc2967f2

yoga/YGNode.h

@@ -270,6 +270,17 @@ typedef void (*YGPrintFunc)(YGNodeConstRef node);
  */
 YG_EXPORT void YGNodeSetPrintFunc(YGNodeRef node, YGPrintFunc printFunc);
 
+/**
+ * Make it so that this node will always form a containing block for any
+ * descendant nodes. This is useful for when a node has a property outside of
+ * of Yoga that will form a containing block. For example, transforms or some of
+ * the others listed in
+ * https://developer.mozilla.org/en-US/docs/Web/CSS/Containing_block
+ */
+YG_EXPORT void YGNodeSetAlwaysFormsContainingBlock(
+    YGNodeRef node,
+    bool alwaysFormsContainingBlock);
+
 /**
  * Print a node to log output.
  */