Moved getLeadingMargin as a function on YGNode

Summary: Moved getLeadingMargin as a function on YGNode

Reviewed By: emilsjolander

Differential Revision: D6683270

fbshipit-source-id: a26663006419e13cb783e9849183e3c665f59b3c

yoga/Utils.h

@@ -53,3 +53,9 @@ inline YGFlexDirection YGResolveFlexDirection(
 
   return flexDirection;
 }
+
+static inline float YGResolveValueMargin(
+    const YGValue value,
+    const float parentSize) {
+  return value.unit == YGUnitAuto ? 0 : YGResolveValue(value, parentSize);
+}