Use a scroll recorder rather than scroll offset for composited-scrolling backgrounds.

third_party/WebKit/Source/core/paint/BoxPainter.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 "core/paint/BoxPainter.h"
 
 #include "core/HTMLNames.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/layout/ImageQualityController.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutTable.h"
 #include "core/layout/LayoutTheme.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/layout/line/RootInlineBox.h"
 #include "core/style/BorderEdge.h"
 #include "core/style/ShadowList.h"
 #include "core/paint/BackgroundImageGeometry.h"
 #include "core/paint/BoxBorderPainter.h"
 #include "core/paint/BoxDecorationData.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/NinePieceImagePainter.h"
 #include "core/paint/PaintInfo.h"
 #include "core/paint/PaintLayer.h"
 #include "core/paint/RoundedInnerRectClipper.h"
+#include "core/paint/ScrollRecorder.h"
 #include "core/paint/ThemePainter.h"
 #include "platform/LengthFunctions.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/geometry/LayoutRectOutsets.h"
 #include "platform/graphics/GraphicsContextStateSaver.h"
 #include "platform/graphics/paint/CompositingDisplayItem.h"
 #include "wtf/Optional.h"
 
 namespace blink {
 
@@ skipping 13 matching lines @@
     LayoutPoint adjustedPaintOffset = paintOffset + m_layoutBox.location();
     // Default implementation. Just pass paint through to the children.
     PaintInfo childInfo(paintInfo);
     for (LayoutObject* child = m_layoutBox.slowFirstChild(); child; child = child->nextSibling())
         child->paint(childInfo, adjustedPaintOffset);
 }
 
 void BoxPainter::paintBoxDecorationBackground(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     LayoutRect paintRect;
+    Optional<ScrollRecorder> scrollRecorder;
     if (isPaintingBackgroundOfPaintContainerIntoScrollingContentsLayer(&m_layoutBox, paintInfo)) {
         // For the case where we are painting the background into the scrolling contents layer
         // of a composited scroller we need to include the entire overflow rect.
         paintRect = m_layoutBox.layoutOverflowRect();
-        paintRect.move(-m_layoutBox.scrolledContentOffset());
+        scrollRecorder.emplace(paintInfo.context, m_layoutBox, paintInfo.phase, m_layoutBox.scrolledContentOffset());
 
         // The background painting code assumes that the borders are part of the paintRect so we
         // expand the paintRect by the border size when painting the background into the
         // scrolling contents layer.
         paintRect.expandEdges(
             LayoutUnit(m_layoutBox.borderTop()),
             LayoutUnit(m_layoutBox.borderRight()),
             LayoutUnit(m_layoutBox.borderBottom()),
             LayoutUnit(m_layoutBox.borderLeft()));
     } else {
@@ skipping 791 matching lines @@
     }
 }
 
 bool BoxPainter::shouldForceWhiteBackgroundForPrintEconomy(const ComputedStyle& style, const Document& document)
 {
     return document.printing() && style.getPrintColorAdjust() == PrintColorAdjustEconomy
         && (!document.settings() || !document.settings()->shouldPrintBackgrounds());
 }
 
 } // namespace blink