[LayoutNG] Initial support for multicol, introducing NGBlockBreakToken.

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 c96ad009c9cbec5e1fa3833d057decdf0ab47ad8..72ca485312fec238711da38e82b32b4f5f8d5500 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
@@ -81,6 +81,12 @@ class CORE_EXPORT NGFragmentBuilder final
   NGFragmentBuilder& AddOutOfFlowDescendant(NGBlockNode*,
                                             const NGStaticPosition&);
 
+  void SetBreakToken(NGBreakToken* token) {
+    DCHECK(!break_token_);
+    break_token_ = token;
+  }
+  bool HasBreakToken() const { return break_token_; }
+
   // Sets MarginStrut for the resultant fragment.
   NGFragmentBuilder& SetMarginStrutBlockStart(const NGMarginStrut& from);
   NGFragmentBuilder& SetMarginStrutBlockEnd(const NGMarginStrut& from);
@@ -132,6 +138,8 @@ class CORE_EXPORT NGFragmentBuilder final
 
   WeakBoxList out_of_flow_descendants_;
   Vector<NGStaticPosition> out_of_flow_positions_;
+
+  Member<NGBreakToken> break_token_;
 };
 
 }  // namespace blink