[SPv2] Track paint offset change

third_party/WebKit/Source/core/paint/ObjectPainter.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 ObjectPainter_h
 #define ObjectPainter_h
 
 #include "core/style/ComputedStyleConstants.h"
+#include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/Allocator.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class Color;
 class GraphicsContext;
 class LayoutPoint;
 struct PaintInfo;
 class LayoutObject;
@@ skipping 34 matching lines @@
   // Also see core/paint/README.md.
   //
   // It is expected that the caller will call this function independent of the
   // value of paintInfo.phase, and this function will do atomic paint (for
   // PaintPhaseForeground), normal paint (for PaintPhaseSelection and
   // PaintPhaseTextClip) or nothing (other paint phases) according to
   // paintInfo.phase.
   void paintAllPhasesAtomically(const PaintInfo&,
                                 const LayoutPoint& paintOffset);
 
+  // When SlimmingPaintInvalidation is enabled, we compute paint offsets during
+  // the pre-paint tree walk (PrePaintTreeWalk). This check verifies that the
+  // paint offset computed during pre-paint matches the actual paint offset
+  // during paint.
+  void checkPaintOffset(const PaintInfo& paintInfo,
+                        const LayoutPoint& paintOffset) {
+#if DCHECK_IS_ON()
+    // For now this works for SPv2 (implying SlimmingPaintInvalidation) only,
+    // but not SlimmingPaintInvalidation on SPv1 because of complexities of
+    // paint invalidation containers in SPv1.
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
+      doCheckPaintOffset(paintInfo, paintOffset);
+#endif
+  }
+
  private:
   static void drawDashedOrDottedBoxSide(GraphicsContext&,
                                         int x1,
                                         int y1,
                                         int x2,
                                         int y2,
                                         BoxSide,
                                         Color,
                                         int thickness,
                                         EBorderStyle,
@@ skipping 25 matching lines @@
                                int x1,
                                int y1,
                                int x2,
                                int y2,
                                BoxSide,
                                Color,
                                int adjacentWidth1,
                                int adjacentWidth2,
                                bool antialias);
 
+#if DCHECK_IS_ON()
+  void doCheckPaintOffset(const PaintInfo&, const LayoutPoint& paintOffset);
+#endif
+
   const LayoutObject& m_layoutObject;
 };
 
 }  // namespace blink
 
 #endif