Fix invalidity in HitTestCache with LayoutParts.

Source/core/layout/LayoutView.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 42 matching lines @@
     void willBeDestroyed() override;
 
     // hitTest() will update layout, style and compositing first while hitTestNoLifecycleUpdate() does not.
     bool hitTest(HitTestResult&);
     bool hitTestNoLifecycleUpdate(HitTestResult&);
 
     // Returns the total count of calls to HitTest, for testing.
     unsigned hitTestCount() const { return m_hitTestCount; }
     unsigned hitTestCacheHits() const { return m_hitTestCacheHits; }
 
-    void clearHitTestCache() { m_hitTestCache->clear(); }
+    void clearHitTestCache();
 
     const char* name() const override { return "LayoutView"; }
 
     bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectLayoutView || LayoutBlockFlow::isOfType(type); }
 
     DeprecatedPaintLayerType layerTypeRequired() const override { return NormalDeprecatedPaintLayer; }
 
     bool isChildAllowed(LayoutObject*, const ComputedStyle&) const override;
 
     void layout() override;
@@ skipping 185 matching lines @@
             m_paintInvalidationState->m_cachedOffsetsEnabled = true;
     }
 private:
     const PaintInvalidationState* m_paintInvalidationState;
     bool m_didDisable;
 };
 
 } // namespace blink
 
 #endif // LayoutView_h