[LayoutNG] Switch NGBreakToken to being RefCounted.

third_party/WebKit/Source/core/layout/ng/ng_physical_fragment.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 NGPhysicalFragment_h
 #define NGPhysicalFragment_h
 
 #include "core/CoreExport.h"
+#include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_units.h"
 #include "platform/LayoutUnit.h"
 #include "platform/heap/Handle.h"
+#include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class ComputedStyle;
 class LayoutObject;
-class NGBreakToken;
 
 // The NGPhysicalFragment contains the output geometry from layout. The
 // fragment stores all of its information in the physical coordinate system for
 // use by paint, hit-testing etc.
 //
 // The fragment keeps a pointer back to the LayoutObject which generated it.
 // Once we have transitioned fully to LayoutNG it should be a const pointer
 // such that paint/hit-testing/etc don't modify it.
 //
 // Layout code should only access geometry information through the
@@ skipping 43 matching lines @@
     return offset_;
   }
 
   // Should only be used by the parent fragement's layout.
   void SetOffset(NGPhysicalOffset offset) {
     DCHECK(!is_placed_);
     offset_ = offset;
     is_placed_ = true;
   }
 
-  NGBreakToken* BreakToken() const { return break_token_; }
+  NGBreakToken* BreakToken() const { return break_token_.get(); }
 
   const ComputedStyle& Style() const;
 
   // GetLayoutObject should only be used when necessary for compatibility
   // with LegacyLayout.
   LayoutObject* GetLayoutObject() const { return layout_object_; }
 
   bool IsPlaced() const { return is_placed_; }
 
  protected:
   NGPhysicalFragment(LayoutObject* layout_object,
                      NGPhysicalSize size,
                      NGPhysicalSize overflow,
                      NGFragmentType type,
-                     NGBreakToken* break_token = nullptr);
+                     RefPtr<NGBreakToken> break_token = nullptr);
 
   LayoutObject* layout_object_;
   NGPhysicalSize size_;
   NGPhysicalSize overflow_;
   NGPhysicalOffset offset_;
-  Persistent<NGBreakToken> break_token_;
+  RefPtr<NGBreakToken> break_token_;
 
   unsigned type_ : 1;
   unsigned is_placed_ : 1;
 
  private:
   void destroy() const;
 };
 
 }  // namespace blink
 
 #endif  // NGPhysicalFragment_h