Implement incremental paint property tree rebuilding

third_party/WebKit/Source/platform/graphics/paint/ScrollPaintPropertyNode.h

 // Copyright 2016 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 ScrollPaintPropertyNode_h
 #define ScrollPaintPropertyNode_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatSize.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
@@ skipping 42 matching lines @@
     m_parent = parent;
     DCHECK(scrollOffsetTranslation->matrix().isIdentityOr2DTranslation());
     m_scrollOffsetTranslation = scrollOffsetTranslation;
     m_clip = clip;
     m_bounds = bounds;
     m_userScrollableHorizontal = userScrollableHorizontal;
     m_userScrollableVertical = userScrollableVertical;
     m_mainThreadScrollingReasons = 0;
   }
 
+  // TODO(pdr): Correctly clone main thread scrolling reasons.
+  PassRefPtr<ScrollPaintPropertyNode> clone() const {
+    return adoptRef(new ScrollPaintPropertyNode(
+        m_parent, m_scrollOffsetTranslation, m_clip, m_bounds,
+        m_userScrollableHorizontal, m_userScrollableVertical));
+  }
+
+  bool operator==(const ScrollPaintPropertyNode& o) const {
+    return m_parent == o.m_parent &&
+           m_scrollOffsetTranslation == o.m_scrollOffsetTranslation &&
+           m_clip == o.m_clip && m_bounds == o.m_bounds &&
+           m_userScrollableHorizontal == o.m_userScrollableHorizontal &&
+           m_userScrollableVertical == o.m_userScrollableVertical &&
+           m_mainThreadScrollingReasons == o.m_mainThreadScrollingReasons;
+  }
+
   ScrollPaintPropertyNode* parent() const { return m_parent.get(); }
   bool isRoot() const { return !m_parent; }
 
   // Transform that the scroll is relative to.
   const TransformPaintPropertyNode* scrollOffsetTranslation() const {
     return m_scrollOffsetTranslation.get();
   }
 
   // The clipped area that contains the scrolled content.
   const IntSize& clip() const { return m_clip; }
@@ skipping 46 matching lines @@
   // TODO(pdr): Add a bit for whether this is affected by page scale.
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const ScrollPaintPropertyNode&, std::ostream*);
 
 }  // namespace blink
 
 #endif  // ScrollPaintPropertyNode_h