[CSS Grid Layout] Implement CSSGridTemplateAreasValue::equals

Source/core/css/CSSGridTemplateAreasValue.cpp

Index: Source/core/css/CSSGridTemplateAreasValue.cpp
diff --git a/Source/core/css/CSSGridTemplateAreasValue.cpp b/Source/core/css/CSSGridTemplateAreasValue.cpp
index 5f527b15663f0ca49f86b4bda35f84610b8a0724..f5ea076384dd715a87b31811677d1fe5501e6b7c 100644
--- a/Source/core/css/CSSGridTemplateAreasValue.cpp
+++ b/Source/core/css/CSSGridTemplateAreasValue.cpp
@@ -81,4 +81,9 @@ String CSSGridTemplateAreasValue::customCSSText() const
     return builder.toString();
 }
 
+bool CSSGridTemplateAreasValue::equals(const CSSGridTemplateAreasValue& other) const
+{
+    return m_gridAreaMap == other.m_gridAreaMap && m_rowCount == other.m_rowCount && m_columnCount == other.m_columnCount;
+}
+
 } // namespace blink