[Slimming Paint] Add *FilterDisplayItem type for slimming paint

Source/core/paint/ViewDisplayListTest.cpp

Index: Source/core/paint/ViewDisplayListTest.cpp
diff --git a/Source/core/paint/ViewDisplayListTest.cpp b/Source/core/paint/ViewDisplayListTest.cpp
index 30c5b23f80a4217ae331865946a1650e7db308bd..5a7e78fad5085247d1eecd848263ea9b35094d5e 100644
--- a/Source/core/paint/ViewDisplayListTest.cpp
+++ b/Source/core/paint/ViewDisplayListTest.cpp
@@ -396,6 +396,5 @@ TEST_F(ViewDisplayListTest, ViewDisplayListTest_UpdateClip)
         TestDisplayItem(secondRenderer, DisplayItem::EndClip));
 }
 
-}
-
-}
+} // anonymous namespace
+} // namespace blink