Generate tests for flex properties

Summary: Generate tests for flex-properties and fix bug where flex basis was not taken into account when parent main dimension was undefined.

Differential Revision: D3771513

fbshipit-source-id: 1b5edc7a28bb26217e8a6d10d1829d9031c3ae2e

CSSLayout/CSSLayout.c

@@ -1040,8 +1040,7 @@ static void layoutNodeImpl(const CSSNodeRef node,
         child->layout.computedFlexBasis =
             fmaxf(child->style.dimensions[CSSDimensionHeight],
                   getPaddingAndBorderAxis(child, CSSFlexDirectionColumn));
-      } else if (!CSSValueIsUndefined(child->style.flexBasis) &&
-                 !CSSValueIsUndefined(availableInnerMainDim)) {
+      } else if (!CSSValueIsUndefined(child->style.flexBasis)) {
         child->layout.computedFlexBasis =
             fmaxf(child->style.flexBasis, getPaddingAndBorderAxis(child, mainAxis));
       } else {