Change the type of flex to YGFloatOptional

Summary: Change the type of flex to YGFloatOptional internally, but keeping the public facing API the same as before

Reviewed By: emilsjolander

Differential Revision: D7211327

fbshipit-source-id: 0d979b6ba00317317b98bbc6e63979c7f1feb2da

yoga/Utils.cpp

@@ -57,3 +57,9 @@ float YGFloatSanitize(const float& val) {
 float YGUnwrapFloatOptional(const YGFloatOptional& op) {
   return op.isUndefined ? YGUndefined : op.value;
 }
+
+bool YGFloatOptionalFloatEquals(
+    const YGFloatOptional& optional,
+    const float& val) {
+  return YGUnwrapFloatOptional(optional) == val;
+}