Add justify-content: space-evenly

Summary:
Adds new ```space-evenly``` for ```justify-content```.

Also adds a typofix in one of the other justify-content tests.

Fixes #657
Closes facebook/yoga#658

Differential Revision: D6407996

Pulled By: emilsjolander

fbshipit-source-id: cc837409e1345624b4bd72c31e25fe68dcb0f6a3

YGEnums.cpp

@@ -121,6 +121,8 @@ const char *YGJustifyToString(const YGJustify value){
       return "space-between";
     case YGJustifySpaceAround:
       return "space-around";
+    case YGJustifySpaceEvenly:
+      return "space-evenly";
   }
   return "unknown";
 }

YGEnums.h

@@ -77,13 +77,14 @@ typedef YG_ENUM_BEGIN(YGFlexDirection) {
 } YG_ENUM_END(YGFlexDirection);
 WIN_EXPORT const char *YGFlexDirectionToString(const YGFlexDirection value);
 
-#define YGJustifyCount 5
-typedef YG_ENUM_BEGIN(YGJustify) {
-  YGJustifyFlexStart,
-  YGJustifyCenter,
-  YGJustifyFlexEnd,
-  YGJustifySpaceBetween,
-  YGJustifySpaceAround,
+#define YGJustifyCount 6
+typedef YG_ENUM_BEGIN(YGJustify){
+    YGJustifyFlexStart,
+    YGJustifyCenter,
+    YGJustifyFlexEnd,
+    YGJustifySpaceBetween,
+    YGJustifySpaceAround,
+    YGJustifySpaceEvenly,
 } YG_ENUM_END(YGJustify);
 WIN_EXPORT const char *YGJustifyToString(const YGJustify value);
 

Yoga.cpp

@@ -2447,6 +2447,11 @@ static void YGNodelayoutImpl(const YGNodeRef node,
             betweenMainDim = 0;
           }
           break;
+        case YGJustifySpaceEvenly:
+          // Space is distributed evenly across all elements
+          betweenMainDim = remainingFreeSpace / (itemsOnLine + 1);
+          leadingMainDim = betweenMainDim;
+          break;
         case YGJustifySpaceAround:
           // Space on the edges is half of the space between elements
           betweenMainDim = remainingFreeSpace / itemsOnLine;