[css-grid] Refactor the extent for baseline alignment computation

third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h

Index: third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h
diff --git a/third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h b/third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h
index 988f220384671d96705065269c15085b880d8b63..675a93cfa82bed6de459bb028348550d2630bbb0 100644
--- a/third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h
+++ b/third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h
@@ -262,6 +262,8 @@ class GridTrackSizingAlgorithmStrategy {
       LayoutBox&,
       GridTrackSizingDirection) const;
   LayoutUnit ComputeTrackBasedSize() const;
+  Optional<LayoutUnit> ExtentForBaselineAlignment(LayoutBox&) const;
+
   GridTrackSizingDirection Direction() const { return algorithm_.direction_; }
   double FindFrUnitSize(const GridSpan& tracks_span,
                         LayoutUnit left_over_space) const;