Ignore zero-height fragments during margin collapsing

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

Index: third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
index cbb9244f0038f59b562f7622091b2d9d0c058a45..f7ef2e236c9daf7dfb89efc16267fb26051ef9a9 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
@@ -10,9 +10,7 @@ NGFragmentBuilder::NGFragmentBuilder(
     NGPhysicalFragmentBase::NGFragmentType type)
     : type_(type),
       writing_mode_(HorizontalTopBottom),
-      direction_(LeftToRight),
-      is_margin_strut_block_start_updated_(false),
-      is_margin_strut_block_end_updated_(false) {}
+      direction_(LeftToRight) {}
 
 NGFragmentBuilder& NGFragmentBuilder::SetWritingMode(
     NGWritingMode writing_mode) {
@@ -56,19 +54,15 @@ NGFragmentBuilder& NGFragmentBuilder::AddChild(NGFragment* child,
 
 NGFragmentBuilder& NGFragmentBuilder::SetMarginStrutBlockStart(
     const NGMarginStrut& from) {
-  DCHECK(!is_margin_strut_block_start_updated_);
   margin_strut_.margin_block_start = from.margin_block_start;
   margin_strut_.negative_margin_block_start = from.negative_margin_block_start;
-  is_margin_strut_block_start_updated_ = true;
   return *this;
 }
 
 NGFragmentBuilder& NGFragmentBuilder::SetMarginStrutBlockEnd(
     const NGMarginStrut& from) {
-  DCHECK(!is_margin_strut_block_end_updated_);
   margin_strut_.margin_block_end = from.margin_block_end;
   margin_strut_.negative_margin_block_end = from.negative_margin_block_end;
-  is_margin_strut_block_end_updated_ = true;
   return *this;
 }