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-cs.js

@@ -105,6 +105,10 @@ CSEmitter.prototype = Object.create(Emitter.prototype, {
   YGEdgeStart:{value:'Start'},
   YGEdgeTop:{value:'Top'},
 
+  YGGutterAll:{value:''},
+  YGGutterColumn:{value:'Column'},
+  YGGutterRow:{value:'Row'},
+
   YGFlexDirectionColumn:{value:'YogaFlexDirection.Column'},
   YGFlexDirectionColumnReverse:{value:'YogaFlexDirection.ColumnReverse'},
   YGFlexDirectionRow:{value:'YogaFlexDirection.Row'},
@@ -251,4 +255,8 @@ CSEmitter.prototype = Object.create(Emitter.prototype, {
   YGNodeStyleSetWidth:{value:function(nodeName, value) {
     this.push(nodeName + '.Width = ' + toCsUnitValue(value) + ';');
   }},
+
+  YGNodeStyleSetGap:{value:function(nodeName, gap, value) {
+    this.push(nodeName + '.' + gap + 'Gap' + ' = ' + toCsUnitValue(value) + ';');
+  }},
 });