Emit dummy display item when recorded picture is empty

Source/platform/graphics/paint/ClipDisplayItem.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 ClipDisplayItem_h
 #define ClipDisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/paint/DisplayItem.h"
@@ skipping 12 matching lines @@
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override;
 
     Vector<RoundedRect>& roundedRectClips() { return m_roundedRectClips; }
 
 protected:
     ClipDisplayItem(DisplayItemClient client, Type type, const IntRect& clipRect)
         : DisplayItem(client, type), m_clipRect(clipRect) { }
 
 private:
 #ifndef NDEBUG
+    virtual const char* name() const override { return "Clip"; }
     virtual void dumpPropertiesAsDebugString(WTF::StringBuilder&) const override;
 #endif
     IntRect m_clipRect;
     Vector<RoundedRect> m_roundedRectClips;
 };
 
 class PLATFORM_EXPORT EndClipDisplayItem : public DisplayItem {
 public:
     static PassOwnPtr<EndClipDisplayItem> create(DisplayItemClient client) { return adoptPtr(new EndClipDisplayItem(client)); }
 
     virtual void replay(GraphicsContext*) override;
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override;
 
 protected:
     EndClipDisplayItem(DisplayItemClient client) : DisplayItem(client, EndClip) { }
+
+private:
+#ifndef NDEBUG
+    virtual const char* name() const override { return "EndClip"; }
+#endif
 };
 
 } // namespace blink
 
 #endif // ClipDisplayItem_h