Emit dummy display item when recorded picture is empty

Source/platform/graphics/paint/ClipDisplayItem.h

Index: Source/platform/graphics/paint/ClipDisplayItem.h
diff --git a/Source/platform/graphics/paint/ClipDisplayItem.h b/Source/platform/graphics/paint/ClipDisplayItem.h
index b2df716348be1f16774bd954614ea8ebc772f5cd..237f22b9cc8a5f715d6eece97db1f99c023492a3 100644
--- a/Source/platform/graphics/paint/ClipDisplayItem.h
+++ b/Source/platform/graphics/paint/ClipDisplayItem.h
@@ -30,6 +30,7 @@ protected:
 
 private:
 #ifndef NDEBUG
+    virtual const char* name() const override { return "Clip"; }
     virtual void dumpPropertiesAsDebugString(WTF::StringBuilder&) const override;
 #endif
     IntRect m_clipRect;
@@ -45,6 +46,11 @@ public:
 
 protected:
     EndClipDisplayItem(DisplayItemClient client) : DisplayItem(client, EndClip) { }
+
+private:
+#ifndef NDEBUG
+    virtual const char* name() const override { return "EndClip"; }
+#endif
 };
 
 } // namespace blink