Enable slimming paint by default (for trybots only)

Source/platform/graphics/paint/DisplayItemListTest.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/DisplayItemList.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/paint/ClipRecorder.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 #include "platform/graphics/paint/DrawingRecorder.h"
 #include <gtest/gtest.h>
 
 namespace blink {
 
 class DisplayItemListTest : public ::testing::Test {
 protected:
     DisplayItemList& displayItemList() { return m_displayItemList; }
     const DisplayItems& newPaintListBeforeUpdate() { return displayItemList().m_newDisplayItems; }
 
 private:
     virtual void SetUp() override
     {
         RuntimeEnabledFeatures::setSlimmingPaintEnabled(true);
     }
     virtual void TearDown() override
     {
-        RuntimeEnabledFeatures::setSlimmingPaintEnabled(false);
+        // RuntimeEnabledFeatures::setSlimmingPaintEnabled(false);
     }
 
     DisplayItemList m_displayItemList;
 };
 
 const DisplayItem::Type foregroundDrawingType = static_cast<DisplayItem::Type>(DisplayItem::DrawingPaintPhaseFirst + 4);
 const DisplayItem::Type backgroundDrawingType = DisplayItem::BoxDecorationBackground;
 const DisplayItem::Type clipType = DisplayItem::ClipFirst;
 
 class TestDisplayItemClient {
@@ skipping 595 matching lines @@
     EXPECT_DISPLAY_LIST(displayItemList().displayItems(), 4,
         TestDisplayItem(multicol, backgroundDrawingType),
         TestDisplayItem(content, foregroundDrawingType),
         TestDisplayItem(content, foregroundDrawingType),
         TestDisplayItem(content, foregroundDrawingType));
     EXPECT_NE(picture1, displayItemList().displayItems()[1].picture());
     EXPECT_NE(picture2, displayItemList().displayItems()[2].picture());
 }
 
 } // namespace blink