[SPInvalidation, SPv2] Compute paint offset for paginated content

third_party/WebKit/Source/core/paint/ObjectPainter.cpp

 // 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.
 
 #include "core/paint/ObjectPainter.h"
 
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutTheme.h"
 #include "core/paint/BoxBorderPainter.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
 #include "core/paint/PaintInfo.h"
+#include "core/paint/PaintLayer.h"
 #include "core/style/BorderEdge.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/GraphicsContextStateSaver.h"
 
 namespace blink {
 
 namespace {
 
 void PaintSingleRectangleOutline(const PaintInfo& paint_info,
@@ skipping 683 matching lines @@
   DCHECK(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
 
   // TODO(pdr): Let painter and paint property tree builder generate the same
   // paint offset for LayoutScrollbarPart. crbug.com/664249.
   if (layout_object_.IsLayoutScrollbarPart())
     return;
 
   LayoutPoint adjusted_paint_offset = paint_offset;
   if (layout_object_.IsBox())
     adjusted_paint_offset += ToLayoutBox(layout_object_).Location();
-  DCHECK(layout_object_.PaintOffset() == adjusted_paint_offset)
-      << " Paint offset mismatch: " << layout_object_.DebugName()
-      << " from PaintPropertyTreeBuilder: "
-      << layout_object_.PaintOffset().ToString()
-      << " from painter: " << adjusted_paint_offset.ToString();
+
+  // Paint offsets don't apply to fragments other than the first,
+  // so disbale these checks for all paginated content.
+  if (!layout_object_.PaintingLayer()->EnclosingPaginationLayer()) {
+    DCHECK(layout_object_.PaintOffset() == adjusted_paint_offset)
+        << " Paint offset mismatch: " << layout_object_.DebugName()
+        << " from PaintPropertyTreeBuilder: "
+        << layout_object_.PaintOffset().ToString()
+        << " from painter: " << adjusted_paint_offset.ToString();
+  }
 }
 #endif
 
 }  // namespace blink