[LayoutNG] Switch NGBreakToken to being RefCounted.

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

 // 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.
 
 #include "core/layout/ng/ng_physical_fragment.h"
 
 #include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_physical_box_fragment.h"
 #include "core/layout/ng/ng_physical_text_fragment.h"
 
 namespace blink {
 
 NGPhysicalFragment::NGPhysicalFragment(LayoutObject* layout_object,
                                        NGPhysicalSize size,
                                        NGPhysicalSize overflow,
                                        NGFragmentType type,
-                                       NGBreakToken* break_token)
+                                       RefPtr<NGBreakToken> break_token)
     : layout_object_(layout_object),
       size_(size),
       overflow_(overflow),
-      break_token_(break_token),
+      break_token_(std::move(break_token)),
       type_(type),
       is_placed_(false) {}
 
 void NGPhysicalFragment::destroy() const {
   if (Type() == kFragmentText)
     delete static_cast<const NGPhysicalTextFragment*>(this);
   else
     delete static_cast<const NGPhysicalBoxFragment*>(this);
 }
 
 const ComputedStyle& NGPhysicalFragment::Style() const {
   DCHECK(layout_object_);
   return layout_object_->styleRef();
 }
 
 }  // namespace blink