Implement Percentage support for gap styles (#1643)

Summary:
X-link: https://github.com/facebook/react-native/pull/44067

X-link: https://github.com/facebook/litho/pull/980

Pull Request resolved: https://github.com/facebook/yoga/pull/1643

Changelog [Internal]:
- Added percentage value for flex layout gap
- Wired up to pass proper available width and height to implement this feature

Reviewed By: NickGerleman

Differential Revision: D56002340

fbshipit-source-id: c0bc86ac70a1391f115c87da99c2ef411535f68b

yoga/style/Style.h

@@ -428,11 +428,9 @@ class YG_EXPORT Style {
         computeInlineEndMargin(axis, Direction::LTR, widthSize);
   }
 
-  float computeGapForAxis(FlexDirection axis) const {
+  float computeGapForAxis(FlexDirection axis, float ownerSize) const {
     auto gap = isRow(axis) ? computeColumnGap() : computeRowGap();
-    // TODO: Validate percentage gap, and expose ability to set percentage to
-    // public API
-    return maxOrDefined(gap.resolve(0.0f /*ownerSize*/).unwrap(), 0.0f);
+    return maxOrDefined(gap.resolve(ownerSize).unwrap(), 0.0f);
   }
 
   bool flexStartMarginIsAuto(FlexDirection axis, Direction direction) const {