Implement the algorithm to test merging and overlap in PaintArtifactCompositor.

third_party/WebKit/Source/platform/graphics/paint/DisplayItemList.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 DisplayItemList_h
 #define DisplayItemList_h
 
 #include "platform/graphics/ContiguousContainer.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "platform/graphics/paint/Transform3DDisplayItem.h"
 #include "wtf/Alignment.h"
 #include "wtf/Assertions.h"
 
 namespace blink {
 
+class JSONArray;
 struct PaintChunk;
 
 // kDisplayItemAlignment must be a multiple of alignof(derived display item) for
 // each derived display item; the ideal value is the least common multiple.
 // Currently the limiting factor is TransformationMatrix (in
 // BeginTransform3DDisplayItem), which requests 16-byte alignment.
 static const size_t kDisplayItemAlignment =
     WTF_ALIGN_OF(BeginTransform3DDisplayItem);
 static const size_t kMaximumDisplayItemSize =
     sizeof(BeginTransform3DDisplayItem);
@@ skipping 35 matching lines @@
     Iterator begin() const { return m_begin; }
     Iterator end() const { return m_end; }
 
    private:
     Iterator m_begin;
     Iterator m_end;
   };
   Range<iterator> itemsInPaintChunk(const PaintChunk&);
   Range<const_iterator> itemsInPaintChunk(const PaintChunk&) const;
 
+  std::unique_ptr<JSONArray> subsequenceAsJSON(size_t beginIndex,
+                                               size_t endIndex,
+                                               bool showPictures,
+                                               bool skipNonDrawings) const;
+
  private:
   Vector<IntRect> m_visualRects;
 };
 
 }  // namespace blink
 
 #endif  // DisplayItemList_h