Fix percentage in flexing parent

Summary:
If we don't measure exactly, percentage values aren't exactly either. Fix for #414.
Closes facebook/yoga#416
Closes facebook/yoga#414

Reviewed By: astreet

Differential Revision: D4604729

Pulled By: emilsjolander

fbshipit-source-id: 66880230073209cbe89668b838c2a82e7f9b34df

Author: woehrl01

ReactCommon/yoga/yoga/Yoga.c

@@ -2045,7 +2045,7 @@ static void YGNodelayoutImpl(const YGNodeRef node,
   }
 
   const bool flexBasisOverflows =
-    measureModeMainDim == YGMeasureModeUndefined ? false : totalFlexBasis > availableInnerMainDim;
+      measureModeMainDim == YGMeasureModeUndefined ? false : totalFlexBasis > availableInnerMainDim;
   if (isNodeFlexWrap && flexBasisOverflows && measureModeMainDim == YGMeasureModeAtMost) {
     measureModeMainDim = YGMeasureModeExactly;
   }
@@ -2338,8 +2338,12 @@ static void YGNodelayoutImpl(const YGNodeRef node,
           childCrossSize = YGValueResolve(currentRelativeChild->resolvedDimensions[dim[crossAxis]],
                                           availableInnerCrossDim) +
                            marginCross;
-          childCrossMeasureMode =
-              YGFloatIsUndefined(childCrossSize) ? YGMeasureModeUndefined : YGMeasureModeExactly;
+          const bool isLoosePercentageMeasurement =
+              currentRelativeChild->resolvedDimensions[dim[crossAxis]]->unit == YGUnitPercent &&
+              measureModeCrossDim != YGMeasureModeExactly;
+          childCrossMeasureMode = YGFloatIsUndefined(childCrossSize) || isLoosePercentageMeasurement
+                                      ? YGMeasureModeUndefined
+                                      : YGMeasureModeExactly;
         }
 
         if (!YGFloatIsUndefined(currentRelativeChild->style.aspectRatio)) {