Refactor root element background painting

Source/core/paint/BoxPainter.h

 // 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.
 
 #ifndef BoxPainter_h
 #define BoxPainter_h
 
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/paint/ObjectPainter.h"
 
 namespace blink {
 
 class BackgroundImageGeometry;
 class FloatRoundedRect;
 class LayoutPoint;
 struct PaintInfo;
 class LayoutBox;
 class LayoutObject;
 
 class BoxPainter {
 public:
     BoxPainter(LayoutBox& layoutBox) : m_layoutBox(layoutBox) { }
     void paint(const PaintInfo&, const LayoutPoint&);
 
     void paintBoxDecorationBackground(const PaintInfo&, const LayoutPoint&);
     void paintMask(const PaintInfo&, const LayoutPoint&);
     void paintClippingMask(const PaintInfo&, const LayoutPoint&);
-    void paintFillLayers(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance = BackgroundBleedNone, SkXfermode::Mode = SkXfermode::kSrcOver_Mode, LayoutObject* backgroundObject = 0);
+
+    typedef Vector<const FillLayer*, 8> FillLayerOcclusionOutputList;
+    // Returns true if the result fill layers have non-associative blending or compositing mode.
+    // (i.e. The rendering will be different without creating isolation group by context.saveLayer().)
+    // Note that the output list will be in top-bottom order.
+    bool calculateFillLayerOcclusionCulling(FillLayerOcclusionOutputList &reversedPaintList, const FillLayer&);
+
+    void paintFillLayers(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance = BackgroundBleedNone, SkXfermode::Mode = SkXfermode::kSrcOver_Mode, LayoutObject* backgroundObject = nullptr);
     void paintMaskImages(const PaintInfo&, const LayoutRect&);
     void paintBoxDecorationBackgroundWithRect(const PaintInfo&, const LayoutPoint&, const LayoutRect&);
-    static void paintFillLayerExtended(LayoutBoxModelObject&, const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance, InlineFlowBox* = 0, const LayoutSize& = LayoutSize(), SkXfermode::Mode = SkXfermode::kSrcOver_Mode, LayoutObject* backgroundObject = 0, bool skipBaseColor = false);
-    static void calculateBackgroundImageGeometry(LayoutBoxModelObject&, const LayoutBoxModelObject* paintContainer, const FillLayer&, const LayoutRect& paintRect, BackgroundImageGeometry&, LayoutObject* = 0);
+    static void paintFillLayerExtended(LayoutBoxModelObject&, const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance, InlineFlowBox* = nullptr, const LayoutSize& = LayoutSize(), SkXfermode::Mode = SkXfermode::kSrcOver_Mode, LayoutObject* backgroundObject = nullptr);
+    static void calculateBackgroundImageGeometry(LayoutBoxModelObject&, const LayoutBoxModelObject* paintContainer, const FillLayer&, const LayoutRect& paintRect, BackgroundImageGeometry&, LayoutObject* backgroundObject = nullptr);
     static InterpolationQuality chooseInterpolationQuality(LayoutObject&, GraphicsContext*, Image*, const void*, const LayoutSize&);
     static bool paintNinePieceImage(LayoutBoxModelObject&, GraphicsContext*, const LayoutRect&, const ComputedStyle&, const NinePieceImage&, SkXfermode::Mode = SkXfermode::kSrcOver_Mode);
     static void paintBorder(LayoutBoxModelObject&, const PaintInfo&, const LayoutRect&, const ComputedStyle&, BackgroundBleedAvoidance = BackgroundBleedNone, bool includeLogicalLeftEdge = true, bool includeLogicalRightEdge = true);
     static void paintBoxShadow(const PaintInfo&, const LayoutRect&, const ComputedStyle&, ShadowStyle, bool includeLogicalLeftEdge = true, bool includeLogicalRightEdge = true);
     static bool shouldAntialiasLines(GraphicsContext*);
     static bool allCornersClippedOut(const FloatRoundedRect& border, const IntRect& clipRect);
 
 private:
     void paintBackground(const PaintInfo&, const LayoutRect&, const Color& backgroundColor, BackgroundBleedAvoidance = BackgroundBleedNone);
-    void paintRootBoxFillLayers(const PaintInfo&);
-    void paintFillLayer(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance, SkXfermode::Mode, LayoutObject* backgroundObject, bool skipBaseColor = false);
-    static void paintRootBackgroundColor(LayoutObject&, const PaintInfo&, const LayoutRect&, const Color&);
+    void paintFillLayer(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance, SkXfermode::Mode, LayoutObject* backgroundObject = nullptr);
     static FloatRoundedRect backgroundRoundedRectAdjustedForBleedAvoidance(LayoutObject&, const LayoutRect&, BackgroundBleedAvoidance, InlineFlowBox*, const LayoutSize&, bool includeLogicalLeftEdge, bool includeLogicalRightEdge);
     static FloatRoundedRect getBackgroundRoundedRect(LayoutObject&, const LayoutRect&, InlineFlowBox*, LayoutUnit inlineBoxWidth, LayoutUnit inlineBoxHeight,
         bool includeLogicalLeftEdge, bool includeLogicalRightEdge);
-    static bool isDocumentElementWithOpaqueBackground(LayoutObject&);
     static void applyBoxShadowForBackground(GraphicsContext*, LayoutObject&);
     static bool fixedBackgroundPaintsInLocalCoordinates(const LayoutObject&);
     static IntSize calculateFillTileSize(const LayoutBoxModelObject&, const FillLayer&, const IntSize& scaledPositioningAreaSize);
 
     LayoutRect boundsForDrawingRecorder(const LayoutPoint& paintOffset);
-    LayoutRect rootBackgroundRect();
 
     // FIXME: this should be const.
     LayoutBox& m_layoutBox;
 };
 
 } // namespace blink
 
 #endif