cc: Move DisplayItem::Raster up to DisplayItemList

ui/compositor/paint_cache.h

Index: ui/compositor/paint_cache.h
diff --git a/ui/compositor/paint_cache.h b/ui/compositor/paint_cache.h
index f8119d09542d79ab4632b11a0f82314aad7d66ff..3f1017298546f5f5481c935c1a277c14804acd2f 100644
--- a/ui/compositor/paint_cache.h
+++ b/ui/compositor/paint_cache.h
@@ -6,6 +6,7 @@
 #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"
@@ -33,8 +34,7 @@ class COMPOSITOR_EXPORT PaintCache {
 
   void SetCache(const cc::DrawingDisplayItem& item);
 
-  bool has_cache_;
-  cc::DrawingDisplayItem display_item_;
+  base::Optional<cc::DrawingDisplayItem> display_item_;
 
   DISALLOW_COPY_AND_ASSIGN(PaintCache);
 };