Implement the algorithm to test merging and overlap in PaintArtifactCompositor.

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h

 // 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.
 
 #ifndef PaintPropertyTreeBuilder_h
 #define PaintPropertyTreeBuilder_h
 
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
 #include "platform/graphics/paint/EffectPaintPropertyNode.h"
 #include "platform/graphics/paint/ScrollPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
+class CompositingReasonFinder;
 class FrameView;
 class LayoutObject;
 
 // The context for PaintPropertyTreeBuilder.
 // It's responsible for bookkeeping tree state in other order, for example, the
 // most recent position container seen.
 struct PaintPropertyTreeBuilderContext {
   // State that propagates on the containing block chain (and so is adjusted
   // when an absolute or fixed position object is encountered).
   struct ContainingBlockContext {
@@ skipping 79 matching lines @@
   void updatePropertiesForSelf(const LayoutObject&,
                                PaintPropertyTreeBuilderContext&);
   // Update the paint properties that affect children of this object (e.g.,
   // scroll offset transform) and ensure the context is up to date.
   void updatePropertiesForChildren(const LayoutObject&,
                                    PaintPropertyTreeBuilderContext&);
 
  private:
   static void updatePaintOffsetTranslation(const LayoutObject&,
                                            PaintPropertyTreeBuilderContext&);
-  static void updateTransform(const LayoutObject&,
-                              PaintPropertyTreeBuilderContext&);
+  void updateTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&);
   static void updateTransformForNonRootSVG(const LayoutObject&,
                                            PaintPropertyTreeBuilderContext&);
   static void updateEffect(const LayoutObject&,
                            PaintPropertyTreeBuilderContext&);
   static void updateCssClip(const LayoutObject&,
                             PaintPropertyTreeBuilderContext&);
   static void updateLocalBorderBoxContext(const LayoutObject&,
                                           PaintPropertyTreeBuilderContext&);
   static void updateScrollbarPaintOffset(const LayoutObject&,
                                          PaintPropertyTreeBuilderContext&);
   static void updateOverflowClip(const LayoutObject&,
                                  PaintPropertyTreeBuilderContext&);
   static void updatePerspective(const LayoutObject&,
                                 PaintPropertyTreeBuilderContext&);
   static void updateSvgLocalToBorderBoxTransform(
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
   static void updateScrollAndScrollTranslation(
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
   static void updateOutOfFlowContext(const LayoutObject&,
                                      PaintPropertyTreeBuilderContext&);
+
+  std::unique_ptr<CompositingReasonFinder> m_compositingReasonFinder;
 };
 
 }  // namespace blink
 
 #endif  // PaintPropertyTreeBuilder_h