[css-grid] Implementing the grid's first line baseline.

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

Index: third_party/WebKit/Source/core/layout/LayoutGrid.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutGrid.h b/third_party/WebKit/Source/core/layout/LayoutGrid.h
index d4d38e9134f5556280b214f1c8b30b55ad720e4c..7001e07b619aaa5cc17485f2b322e404048b1e92 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.h
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.h
@@ -299,6 +299,15 @@ class LayoutGrid final : public LayoutBlock {
   bool hasAutoMarginsInRowAxis(const LayoutBox&) const;
   void updateAutoMarginsInColumnAxisIfNeeded(LayoutBox&);
   void updateAutoMarginsInRowAxisIfNeeded(LayoutBox&);
+  LayoutUnit firstLineBoxBaselineForChild(const LayoutBox&) const;
+
+  int baselinePosition(
+      FontBaseline,
+      bool firstLine,
+      LineDirectionMode,
+      LinePositionMode = PositionOnContainingLine) const override;
+  int firstLineBoxBaseline() const override;
+  int inlineBlockBaseline(LineDirectionMode) const override;
 
 #if ENABLE(ASSERT)
   bool tracksAreWiderThanMinTrackBreadth(GridTrackSizingDirection,