Summary:
Adds unit tests that directly cover the order in which `LayoutableChildren` iterator goes over the descendant nodes. The covered cases are as follows (nodes with `display: contents` are marked green):
### Single `display: contents` node
```mermaid
flowchart TD
R((R)) --> A((A))
R --> B((B))
R --> C((C))
B --> D((D))
B --> E((E))
style B fill:https://github.com/facebook/yoga/issues/090
```
Correct order: `A, D, E, C`
### Multiple `display: contents` nodes
```mermaid
flowchart TD
R((R)) --> A((A))
R --> B((B))
R --> C((C))
A --> D((D))
A --> E((E))
B --> F((F))
B --> G((G))
C --> H((H))
C --> I((I))
style A fill:https://github.com/facebook/yoga/issues/090
style B fill:https://github.com/facebook/yoga/issues/090
style C fill:https://github.com/facebook/yoga/issues/090
```
Correct order: `D, E, F, G, H, I`
### Nested `display: contents` nodes
```mermaid
flowchart TD
R((R)) --> A((A))
R --> B((B))
R --> C((C))
B --> D((D))
B --> E((E))
E --> F((F))
E --> G((G))
style B fill:https://github.com/facebook/yoga/issues/090
style E fill:https://github.com/facebook/yoga/issues/090
```
Correct order: `A, D, F, G, C`
### Leaf `display: contents` node
```mermaid
flowchart TD
R((R)) --> A((A))
R --> B((B))
R --> C((C))
style B fill:https://github.com/facebook/yoga/issues/090
```
Correct order: `A, C`
### Root `display: contents` node
```mermaid
flowchart TD
R((R)) --> A((A))
R --> B((B))
R --> C((C))
style R fill:https://github.com/facebook/yoga/issues/090
```
Correct order: `A, B, C` - `LayoutableChildren` goes over the children with `display: contents` property, setting it on the root node should have no effect.
Changelog: [Internal]
Pull Request resolved: https://github.com/facebook/yoga/pull/1731
Reviewed By: joevilches
Differential Revision: D64981779
Pulled By: NickGerleman
fbshipit-source-id: ee39759c663a40f96ad313f1b775d53ab68fb442
