Do not collapse margins with padding/border b/w parent and first/last child

third_party/WebKit/Source/core/layout/ng/ng_units.cc

Index: third_party/WebKit/Source/core/layout/ng/ng_units.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_units.cc b/third_party/WebKit/Source/core/layout/ng/ng_units.cc
index 4f45a68dcab327a8166c123a649c9dae56847d6a..771ed654dcb856099ac0a8695156ed50a802ad6f 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_units.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_units.cc
@@ -79,6 +79,14 @@ void NGMarginStrut::AppendMarginBlockEnd(const LayoutUnit& value) {
   }
 }
 
+void NGMarginStrut::SetMarginBlockStart(const LayoutUnit& value) {
+  if (value < 0) {
+    negative_margin_block_start = value;
+  } else {
+    margin_block_start = value;
+  }
+}
+
 void NGMarginStrut::SetMarginBlockEnd(const LayoutUnit& value) {
   if (value < 0) {
     negative_margin_block_end = value;