Rewrite how paint properties are built with bg:fixed main thread scrolling

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.cpp

 // Copyright 2015 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 "core/paint/PaintPropertyTreeBuilderTest.h"
 
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutTreeAsText.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintPropertyTreePrinter.h"
@@ skipping 2855 matching lines @@
       "  .forceScroll {"
       "    height: 4000px;"
       "  }"
       "</style>"
       "<div id='overflow'>"
       "  <div class='backgroundAttachmentFixed'></div>"
       "</div>"
       "<div class='forceScroll'></div>");
   Element* overflow = document().getElementById("overflow");
   EXPECT_TRUE(frameScroll()->hasBackgroundAttachmentFixedDescendants());
-  EXPECT_TRUE(overflow->layoutObject()
-                  ->paintProperties()
-                  ->scroll()
-                  ->hasBackgroundAttachmentFixedDescendants());
+  // No scroll node is needed.
+  EXPECT_EQ(overflow->layoutObject()->paintProperties()->scroll(), nullptr);
 }
 
 TEST_P(PaintPropertyTreeBuilderTest, PaintOffsetsUnderMultiColumn) {
   setBodyInnerHTML(
       "<style>"
       "  body { margin: 0; }"
       "  .space { height: 30px; }"
       "  .abs { position: absolute; width: 20px; height: 20px; }"
       "</style>"
       "<div style='columns:2; width: 200px; column-gap: 0'>"
@@ skipping 254 matching lines @@
 
   LayoutObject* target = getLayoutObjectByElementId("target");
   const auto* localBorderBoxProperties =
       target->paintProperties()->localBorderBoxProperties();
   ASSERT_TRUE(localBorderBoxProperties);
   EXPECT_EQ(LayoutPoint(66, 55), target->paintOffset());
   EXPECT_EQ(effect, localBorderBoxProperties->effect());
 }
 
 }  // namespace blink