Slimming Paint phase 2 compositing algorithm plumbing & skeleton display list API.

Source/platform/graphics/paint/DisplayItem.h

 // Copyright 2014 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 DisplayItem_h
 #define DisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/ListContainer.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
+#include "public/platform/WebDisplayList.h"
 #include "wtf/Assertions.h"
 #include "wtf/PassOwnPtr.h"
 
 #ifndef NDEBUG
 #include "wtf/text/StringBuilder.h"
 #include "wtf/text/WTFString.h"
 #endif
 
 
 namespace blink {
 
 class GraphicsContext;
 class WebDisplayItemList;
 
-class PLATFORM_EXPORT DisplayItem {
+class PLATFORM_EXPORT DisplayItem : public WebDisplayItem {
 public:
     enum {
         // Must be kept in sync with core/paint/PaintPhase.h.
         PaintPhaseMax = 12,
     };
 
     // A display item type uniquely identifies a display item of a client.
     // Some display item types can be categorized using the following directives:
     // - In enum Type:
     //   - enum value <Category>First;
@@ skipping 329 matching lines @@
     bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
 #endif
 
 private:
     bool isEnd() const final { return true; }
 };
 
 } // namespace blink
 
 #endif // DisplayItem_h