[Slimming Paint] Add *FilterDisplayItem type for slimming paint

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/ViewDisplayList.h"
 
 #include "core/paint/ClipRecorder.h"
 #include "core/paint/DrawingRecorder.h"
 #include "core/rendering/RenderView.h"
@@ skipping 378 matching lines @@
         drawRect(context, secondRenderer, PaintPhaseBlockBackground, FloatRect(100, 100, 150, 150));
     }
 
     EXPECT_DISPLAY_LIST(renderView()->viewDisplayList().paintList(), 4,
         TestDisplayItem(firstRenderer, DisplayItem::DrawingPaintPhaseBlockBackground),
         TestDisplayItem(secondRenderer, DisplayItem::ClipLayerForeground),
         TestDisplayItem(secondRenderer, DisplayItem::DrawingPaintPhaseBlockBackground),
         TestDisplayItem(secondRenderer, DisplayItem::EndClip));
 }
 
-}
-
-}
+} // anonymous namespace
+} // namespace blink