Emit dummy display item when recorded picture is empty

Source/platform/graphics/paint/TransformDisplayItem.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 TransformDisplayItem_h
 #define TransformDisplayItem_h
 
 #include "platform/graphics/paint/DisplayItem.h"
 #include "platform/transforms/TransformationMatrix.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace blink {
 
 class TransformationMatrix;
 
 class PLATFORM_EXPORT BeginTransformDisplayItem : public DisplayItem {
 public:
     static PassOwnPtr<BeginTransformDisplayItem> create(DisplayItemClient client, const TransformationMatrix& matrix) { return adoptPtr(new BeginTransformDisplayItem(client, matrix)); }
 
     virtual void replay(GraphicsContext*) override;
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override;
 
 protected:
     BeginTransformDisplayItem(DisplayItemClient, const TransformationMatrix&);
 
 private:
+#ifndef NDEBUG
+    virtual const char* name() const override { return "BeginTransform"; }
+#endif
+
     const TransformationMatrix m_transform;
 };
 
 class PLATFORM_EXPORT EndTransformDisplayItem : public DisplayItem {
 public:
     static PassOwnPtr<EndTransformDisplayItem> create(DisplayItemClient client) { return adoptPtr(new EndTransformDisplayItem(client)); }
 
     virtual void replay(GraphicsContext*) override;
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override;
 
 protected:
     EndTransformDisplayItem(DisplayItemClient client)
         : DisplayItem(client, EndTransform) { }
+
+private:
+#ifndef NDEBUG
+    virtual const char* name() const override { return "EndTransform"; }
+#endif
 };
 
 } // namespace blink
 
 #endif // TransformDisplayItem_h