Emit dummy display item when recorded picture is empty

Source/core/paint/ViewDisplayListTest.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 "core/paint/LayerClipRecorder.h"
 #include "core/paint/RenderDrawingRecorder.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/RenderingTestHelper.h"
@@ skipping 28 matching lines @@
 
     RenderView* m_renderView;
 };
 
 class TestDisplayItem : public DisplayItem {
 public:
     TestDisplayItem(const RenderObject* renderer, Type type) : DisplayItem(renderer->displayItemClient(), type) { }
 
     virtual void replay(GraphicsContext*) override final { ASSERT_NOT_REACHED(); }
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const override final { ASSERT_NOT_REACHED(); }
+#ifndef NDEBUG
+    virtual const char* name() const override final { return "Test"; }
+#endif
 };
 
 #define EXPECT_DISPLAY_LIST(actual, expectedSize, ...) { \
     EXPECT_EQ((size_t)expectedSize, actual.size()); \
     const TestDisplayItem expected[] = { __VA_ARGS__ }; \
     for (size_t index = 0; index < expectedSize; index++) { \
         EXPECT_EQ(expected[index].client(), actual[index]->client()); \
         EXPECT_EQ(expected[index].type(), actual[index]->type()); \
     } \
 }
@@ skipping 378 matching lines @@
     EXPECT_TRUE(rootDisplayItemList().clientCacheIsValid(firstRenderer->displayItemClient()));
     EXPECT_TRUE(rootDisplayItemList().clientCacheIsValid(secondRenderer->displayItemClient()));
 
     rootDisplayItemList().invalidateAll();
     EXPECT_FALSE(rootDisplayItemList().clientCacheIsValid(firstRenderer->displayItemClient()));
     EXPECT_FALSE(rootDisplayItemList().clientCacheIsValid(secondRenderer->displayItemClient()));
 }
 
 } // anonymous namespace
 } // namespace blink