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-cpp.js

@@ -92,6 +92,10 @@ CPPEmitter.prototype = Object.create(Emitter.prototype, {
   YGEdgeStart:{value:'YGEdgeStart'},
   YGEdgeTop:{value:'YGEdgeTop'},
 
+  YGGutterAll:{value:'YGGutterAll'},
+  YGGutterColumn:{value:'YGGutterColumn'},
+  YGGutterRow:{value:'YGGutterRow'},
+
   YGFlexDirectionColumn:{value:'YGFlexDirectionColumn'},
   YGFlexDirectionColumnReverse:{value:'YGFlexDirectionColumnReverse'},
   YGFlexDirectionRow:{value:'YGFlexDirectionRow'},
@@ -242,4 +246,8 @@ CPPEmitter.prototype = Object.create(Emitter.prototype, {
   YGNodeStyleSetWidth:{value:function(nodeName, value) {
     this.push('YGNodeStyleSetWidth' + toFunctionName(value) + '(' + nodeName + ', ' + toValueCpp(value) + ');');
   }},
+
+  YGNodeStyleSetGap:{value:function(nodeName, gap, value) {
+    this.push('YGNodeStyleSetGap' + toFunctionName(value) + '(' + nodeName + ', ' + gap + ', ' + toValueCpp(value) + ');');
+  }},
 });