cc: Move DisplayItem::Raster up to DisplayItemList

ui/compositor/paint_cache.h

 // Copyright 2015 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 UI_COMPOSITOR_PAINT_CACHE_H_
 #define UI_COMPOSITOR_PAINT_CACHE_H_
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "cc/playback/drawing_display_item.h"
 #include "ui/compositor/compositor_export.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace ui {
 class PaintContext;
 class PaintRecorder;
 
 // A class that holds the output of a PaintRecorder to be reused when the
 // object that created the PaintRecorder has not been changed/invalidated.
 class COMPOSITOR_EXPORT PaintCache {
  public:
   PaintCache();
   ~PaintCache();
 
   // Returns true if the PaintCache was able to insert a previously-saved
   // painting output into the PaintContext. If it returns false, the caller
   // needs to do the work of painting, which can be stored into the PaintCache
   // to be used next time.
   bool UseCache(const PaintContext& context, const gfx::Size& size_in_context);
 
  private:
   // Only PaintRecorder can modify these.
   friend PaintRecorder;
 
   void SetCache(const cc::DrawingDisplayItem& item);
 
-  bool has_cache_;
-  cc::DrawingDisplayItem display_item_;
+  base::Optional<cc::DrawingDisplayItem> display_item_;
 
   DISALLOW_COPY_AND_ASSIGN(PaintCache);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_PAINT_CACHE_H_