Teach test generator gap/row-gap/column-gap

Summary:
This adds mappings to the test generator to create the right language specific calls when an HTML fixture has gap properties.

Changelog:
[Internal][Added] - Teach yoga test generator gap/row-gap/column-gap

Reviewed By: javache

Differential Revision: D39922409

fbshipit-source-id: 5b905ed95ae64373d2c7d3bb1a03e94270bf209a

gentest/gentest.js

@@ -165,6 +165,15 @@ function setupTestTree(e, parent, node, genericNode, nodeName, parentName, index
 
     if (!isDefaultStyleValue(style, node.style[style])) {
       switch (style) {
+        case 'gap':
+          e.YGNodeStyleSetGap(nodeName, e.YGGutterAll, pointValue(e, node.style[style]));
+          break;
+        case 'column-gap':
+          e.YGNodeStyleSetGap(nodeName, e.YGGutterColumn, pointValue(e, node.style[style]));
+          break;
+        case 'row-gap':
+          e.YGNodeStyleSetGap(nodeName, e.YGGutterRow, pointValue(e, node.style[style]));
+          break;
         case 'direction':
           e.YGNodeStyleSetDirection(nodeName, directionValue(e, node.style[style]));
           break;
@@ -477,6 +486,8 @@ function calculateTree(root, roundToPixelGrid) {
 }
 
 function getYogaStyle(node) {
+  // TODO: Relying on computed style means we cannot test shorthand props like
+  // "padding", "margin", "gap".
   return [
     'direction',
     'flex-direction',
@@ -512,6 +523,8 @@ function getYogaStyle(node) {
     'height',
     'min-height',
     'max-height',
+    'column-gap',
+    'row-gap',
     'display',
   ].reduce(function(map, key) {
     map[key] = node.style[key] || getComputedStyle(node, null).getPropertyValue(key);