FontCachePurgePreventer is needed when computing MinPreferredWidth

third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.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 LayoutNGBlockFlow_h
 #define LayoutNGBlockFlow_h
 
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/ng/ng_block_node.h"
 
 namespace blink {
 
 // This overrides the default layout block algorithm to use Layout NG.
 class LayoutNGBlockFlow final : public LayoutBlockFlow {
  public:
   explicit LayoutNGBlockFlow(Element*);
   ~LayoutNGBlockFlow() override = default;
 
   void layoutBlock(bool relayoutChildren) override;
   NGBlockNode* boxForTesting() const { return m_box.get(); }
 
+ protected:
+  void computeIntrinsicLogicalWidths(
+      LayoutUnit& minLogicalWidth,
+      LayoutUnit& maxLogicalWidth) const override;
+
  private:
   bool isOfType(LayoutObjectType) const override;
 
   Persistent<NGBlockNode> m_box;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutNGBlockFlow, isLayoutNGBlockFlow());
 
 }  // namespace blink
 
 #endif  // LayoutNGBlockFlow_h