Emit dummy display item when recorded picture is empty

Source/platform/graphics/paint/DisplayItem.cpp

 // 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.
 
 #include "config.h"
 #include "platform/graphics/paint/DisplayItem.h"
 
 namespace blink {
 
+namespace {

[pdr., 2014/12/12 18:39:04]

Does this need to be in a namespace block?

+
+class DummyDisplayItem : public DisplayItem {
+public:
+    DummyDisplayItem(DisplayItemClient client, Type type) : DisplayItem(client, type) { }
+
+private:
+    virtual void replay(GraphicsContext*) override final { }
+    virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override final { }
+    virtual const char* name() const override final { return "Dummy"; }
+};
+
+} // namespace
+
+PassOwnPtr<DisplayItem> DisplayItem::createDummy(DisplayItemClient client, Type type)
+{
+    return adoptPtr(new DummyDisplayItem(client, type));
+}
+
 #ifndef NDEBUG
 
 WTF::String DisplayItem::typeAsDebugString(DisplayItem::Type type)
 {
     switch (type) {
     case DisplayItem::DrawingPaintPhaseBlockBackground: return "DrawingPaintPhaseBlockBackground";
     case DisplayItem::DrawingPaintPhaseChildBlockBackground: return "DrawingPaintPhaseChildBlockBackground";
     case DisplayItem::DrawingPaintPhaseChildBlockBackgrounds: return "DrawingPaintPhaseChildBlockBackgrounds";
     case DisplayItem::DrawingPaintPhaseFloat: return "DrawingPaintPhaseFloat";
     case DisplayItem::DrawingPaintPhaseForeground: return "DrawingPaintPhaseForeground";
@@ skipping 47 matching lines @@
 {
     WTF::StringBuilder stringBuilder;
     stringBuilder.append('{');
     dumpPropertiesAsDebugString(stringBuilder);
     stringBuilder.append('}');
     return stringBuilder.toString();
 }
 
 void DisplayItem::dumpPropertiesAsDebugString(WTF::StringBuilder& stringBuilder) const
 {
+    stringBuilder.append("name: \"");
+    stringBuilder.append(name());
+    stringBuilder.append("\", ");
     if (!clientDebugString().isEmpty()) {
         stringBuilder.append(clientDebugString());
         stringBuilder.append(", ");
     }
     stringBuilder.append("type: \"");
-    if (isCached())

[pdr., 2014/12/12 18:39:04]

Any reason for removing this?

[Xianzhu, 2014/12/12 19:11:17]

Now the new "name" attribute can show the same information, so this becomes
redundant.

-        stringBuilder.append("Cached-");
     stringBuilder.append(typeAsDebugString(type()));
     stringBuilder.append('"');
 }
 
 #endif
 
 } // namespace blink