[css-grid] Implement grid gutters

Source/core/style/StyleGridData.h

Index: Source/core/style/StyleGridData.h
diff --git a/Source/core/style/StyleGridData.h b/Source/core/style/StyleGridData.h
index 37f6c534cc3db3c9552ff48c0e29a0c28d7c1d6d..fa024e2cd03107a6e82500b2cf837def71022a0c 100644
--- a/Source/core/style/StyleGridData.h
+++ b/Source/core/style/StyleGridData.h
@@ -46,7 +46,7 @@ public:
 
     bool operator==(const StyleGridData& o) const
     {
-        return m_gridTemplateColumns == o.m_gridTemplateColumns && m_gridTemplateRows == o.m_gridTemplateRows && m_gridAutoFlow == o.m_gridAutoFlow && m_gridAutoRows == o.m_gridAutoRows && m_gridAutoColumns == o.m_gridAutoColumns && m_namedGridColumnLines == o.m_namedGridColumnLines && m_namedGridRowLines == o.m_namedGridRowLines && m_orderedNamedGridColumnLines == o.m_orderedNamedGridColumnLines && m_orderedNamedGridRowLines == o.m_orderedNamedGridRowLines && m_namedGridArea == o.m_namedGridArea && m_namedGridArea == o.m_namedGridArea && m_namedGridAreaRowCount == o.m_namedGridAreaRowCount && m_namedGridAreaColumnCount == o.m_namedGridAreaColumnCount;
+        return m_gridTemplateColumns == o.m_gridTemplateColumns && m_gridTemplateRows == o.m_gridTemplateRows && m_gridAutoFlow == o.m_gridAutoFlow && m_gridAutoRows == o.m_gridAutoRows && m_gridAutoColumns == o.m_gridAutoColumns && m_namedGridColumnLines == o.m_namedGridColumnLines && m_namedGridRowLines == o.m_namedGridRowLines && m_orderedNamedGridColumnLines == o.m_orderedNamedGridColumnLines && m_orderedNamedGridRowLines == o.m_orderedNamedGridRowLines && m_namedGridArea == o.m_namedGridArea && m_namedGridArea == o.m_namedGridArea && m_namedGridAreaRowCount == o.m_namedGridAreaRowCount && m_namedGridAreaColumnCount == o.m_namedGridAreaColumnCount && m_gridColumnGap == o.m_gridColumnGap && m_gridRowGap == o.m_gridRowGap;
     }
 
     bool operator!=(const StyleGridData& o) const
@@ -76,6 +76,9 @@ public:
     size_t m_namedGridAreaRowCount;
     size_t m_namedGridAreaColumnCount;
 
+    Length m_gridColumnGap;
+    Length m_gridRowGap;
+
 private:
     StyleGridData();
     StyleGridData(const StyleGridData&);