Add data-disabled to test fixtures

Summary:
This can be marked in fixtures to skip a test without commenting it out. We add one more usage of this.

The same functionality existed (unused) before for `experiments`, which I changed to `data-experiments`.

Formatting of JS tests changed to be closer to what Prettier would output, and to remove usage of `Yoga.UNDEFINED` which doesn't existi and just resolves to `undefined` (this is converted to NaN by the wrapper layer).

Differential Revision: D45723003

fbshipit-source-id: c014e1695d90fcb44d62f6a636ddbb0d86ec6eff

gentest/gentest.js

@@ -68,7 +68,11 @@ function printTest(e, ext, LTRContainer, RTLContainer, genericContainer) {
 
 
   for (var i = 0; i < genericLayoutTree.length; i++) {
-    e.emitTestPrologue(genericLayoutTree[i].name, genericLayoutTree[i].experiments);
+    e.emitTestPrologue(
+      genericLayoutTree[i].name,
+      genericLayoutTree[i].experiments,
+      genericLayoutTree[i].disabled
+    );
 
     if (genericLayoutTree[i].name == 'wrap_column') {
       // Modify width and left values due to both safari and chrome not abiding by the
@@ -475,9 +479,10 @@ function calculateTree(root, roundToPixelGrid) {
       style: getYogaStyle(child),
       declaredStyle: child.style,
       rawStyle: child.getAttribute('style'),
-      experiments: child.getAttribute('experiments')
-          ? child.getAttribute('experiments').split(' ')
+      experiments: child.dataset.experiments
+          ? child.dataset.experiments.split(' ')
           : DEFAULT_EXPERIMENTS,
+      disabled: child.dataset.disabled === 'true',
     };
 
     var size = getRoundedSize(child);