Fix test util to measure text properly based on flex direction (#1768)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1768

Depending on the flex direction text will either be capped to the measured size or to the longest word, so I added that functionality

Reviewed By: mlord93

Differential Revision: D67106199

fbshipit-source-id: 0b4691768809004043a847f3fc5f7b94e92f1575

gentest/gentest.js

@@ -533,7 +533,11 @@ function setupTestTree(
   }
 
   if (node.innerText && node.children.length === 0) {
-    e.YGNodeSetMeasureFunc(nodeName, node.innerText);
+    e.YGNodeSetMeasureFunc(
+      nodeName,
+      node.innerText,
+      flexDirectionValue(e, node.style['flex-direction']),
+    );
   }
 
   for (let i = 0; i < node.children.length; i++) {