[LayoutNG] Switch NGBreakToken to being RefCounted.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NGBreakToken_h
 #define NGBreakToken_h
 
 #include "core/CoreExport.h"
+#include "core/layout/ng/ng_layout_input_node.h"
 #include "platform/heap/Handle.h"
+#include "wtf/RefCounted.h"
 
 namespace blink {
 
-class NGLayoutInputNode;
-
 // A break token is a continuation token for layout. A single layout input node
 // can have multiple fragments asssociated with it.
 //
 // Each fragment has a break token which can be used to determine if a layout
 // input node has finished producing fragments (aka. is "exhausted" of
 // fragments), and optionally used to produce the next fragment in the chain.
 //
 // See CSS Fragmentation (https://drafts.csswg.org/css-break/) for a detailed
 // description of different types of breaks which can occur in CSS.
 //
 // Each layout algorithm which can fragment, e.g. block-flow can optionally
 // accept a break token. For example:
 //
 // NGLayoutInputNode* node = ...;
 // NGPhysicalFragment* fragment = node->Layout(space);
 // DCHECK(!fragment->BreakToken()->IsFinished());
 // NGPhysicalFragment* fragment2 = node->Layout(space, fragment->BreakToken());
 //
 // The break token should encapsulate enough information to "resume" the layout.
-class CORE_EXPORT NGBreakToken
-    : public GarbageCollectedFinalized<NGBreakToken> {
+class CORE_EXPORT NGBreakToken : public RefCounted<NGBreakToken> {
  public:
   virtual ~NGBreakToken() {}
 
   enum NGBreakTokenType { kBlockBreakToken, kTextBreakToken };
   NGBreakTokenType Type() const { return static_cast<NGBreakTokenType>(type_); }
 
   enum NGBreakTokenStatus { kUnfinished, kFinished };
 
   // Whether the layout node cannot produce any more fragments.
   bool IsFinished() const { return status_ == kFinished; }
 
   // Returns the node associated with this break token. A break token cannot be
   // used with any other node.
   NGLayoutInputNode* InputNode() const { return node_; }
 
-  DEFINE_INLINE_VIRTUAL_TRACE() { visitor->trace(node_); }
-
  protected:
   NGBreakToken(NGBreakTokenType type,
                NGBreakTokenStatus status,
                NGLayoutInputNode* node)
       : type_(type), status_(status), node_(node) {}
 
  private:
   unsigned type_ : 1;
   unsigned status_ : 1;
 
-  Member<NGLayoutInputNode> node_;
+  Persistent<NGLayoutInputNode> node_;
 };
 
 }  // namespace blink
 
 #endif  // NGBreakToken_h