Initial implementation of Collapsing Margins computational logic for LayoutNG

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

Index: third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
index d524b3625fa451727cd962485bd367e715cee296..998a2aa8fe1e10f6d3164c892b70c839608de132 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
@@ -26,6 +26,12 @@ class CORE_EXPORT NGFragmentBuilder final
 
   NGFragmentBuilder& AddChild(NGFragment*, NGLogicalOffset);
 
+  // Sets MarginStrut for the resultant fragment.
+  // These 2 methods below should be only called once as we update the
+  // fragment's MarginStrut block start/end from first/last children MarginStrut
+  NGFragmentBuilder& SetMarginStrutBlockStart(const NGMarginStrut& from);
+  NGFragmentBuilder& SetMarginStrutBlockEnd(const NGMarginStrut& from);
+
   // Offsets are not supposed to be set during fragment construction, so we
   // do not provide a setter here.
 
@@ -42,8 +48,15 @@ class CORE_EXPORT NGFragmentBuilder final
   NGLogicalSize size_;
   NGLogicalSize overflow_;
 
+  NGMarginStrut margin_strut_;
+
   HeapVector<Member<NGPhysicalFragmentBase>> children_;
   Vector<NGLogicalOffset> offsets_;
+
+  // Whether MarginStrut block start/end was updated.
+  // It's used for DCHECK safety check.
+  bool is_margin_strut_block_start_updated_ : 1;
+  bool is_margin_strut_block_end_updated_ : 1;
 };
 
 }  // namespace blink