[SPInvalidation, SPv2] Compute paint offset for paginated content

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
index 09c25f88501dfaaccb70aa53b710247eaaa7ce0a..7bfe9f4ed16faf04f624ae730491d1669f77cd96 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.cpp
@@ -204,6 +204,7 @@ void PaintPropertyTreeBuilder::UpdateProperties(
   auto* fixed_scroll_node = context.current.scroll;
   DCHECK(frame_view.PreTranslation());
   context.current.transform = frame_view.PreTranslation();
+  context.current.transform_paint_layer = frame_view.GetLayoutView()->Layer();
   DCHECK(frame_view.ContentClip());
   context.current.clip = frame_view.ContentClip();
   if (const auto* scroll_translation = frame_view.ScrollTranslation()) {
@@ -266,11 +267,15 @@ void PaintPropertyTreeBuilder::UpdatePaintOffsetTranslation(
       context.current.rendering_context_id);
 
   context.current.transform = properties.PaintOffsetTranslation();
+  context.current.transform_paint_layer = object.Layer();
+
   context.current.paint_offset = fractional_paint_offset;
   if (RuntimeEnabledFeatures::rootLayerScrollingEnabled() &&
       object.IsLayoutView()) {
     context.absolute_position.transform = properties.PaintOffsetTranslation();
+    context.absolute_position.transform_paint_layer = object.Layer();
     context.fixed_position.transform = properties.PaintOffsetTranslation();
+    context.fixed_position.transform_paint_layer = object.Layer();
     context.absolute_position.paint_offset = LayoutPoint();
     context.fixed_position.paint_offset = LayoutPoint();
   }
@@ -307,6 +312,7 @@ void PaintPropertyTreeBuilder::UpdateTransformForNonRootSVG(
 
   if (object.PaintProperties() && object.PaintProperties()->Transform()) {
     context.current.transform = object.PaintProperties()->Transform();
+    context.current.transform_paint_layer = nullptr;
     context.current.should_flatten_inherited_transform = false;
     context.current.rendering_context_id = 0;
   }
@@ -408,6 +414,10 @@ void PaintPropertyTreeBuilder::UpdateTransform(
   const auto* properties = object.PaintProperties();
   if (properties && properties->Transform()) {
     context.current.transform = properties->Transform();
+    if (object.IsBoxModelObject()) {
+      context.current.transform_paint_layer =
+          ToLayoutBoxModelObject(object).Layer();
+    }
     if (object.StyleRef().Preserves3D()) {
       context.current.rendering_context_id =
           properties->Transform()->RenderingContextId();
@@ -818,6 +828,10 @@ void PaintPropertyTreeBuilder::UpdatePerspective(
   const auto* properties = object.PaintProperties();
   if (properties && properties->Perspective()) {
     context.current.transform = properties->Perspective();
+    if (object.IsBoxModelObject()) {
+      context.current.transform_paint_layer =
+          ToLayoutBoxModelObject(object).Layer();
+    }
     context.current.should_flatten_inherited_transform = false;
   }
 }
@@ -849,6 +863,10 @@ void PaintPropertyTreeBuilder::UpdateSvgLocalToBorderBoxTransform(
   const auto* properties = object.PaintProperties();
   if (properties && properties->SvgLocalToBorderBoxTransform()) {
     context.current.transform = properties->SvgLocalToBorderBoxTransform();
+    if (object.IsBoxModelObject()) {
+      context.current.transform_paint_layer =
+          ToLayoutBoxModelObject(object).Layer();
+    }
     context.current.should_flatten_inherited_transform = false;
     context.current.rendering_context_id = 0;
   }
@@ -932,6 +950,10 @@ void PaintPropertyTreeBuilder::UpdateScrollAndScrollTranslation(
   if (object.PaintProperties() &&
       object.PaintProperties()->ScrollTranslation()) {
     context.current.transform = object.PaintProperties()->ScrollTranslation();
+    if (object.IsBoxModelObject()) {
+      context.current.transform_paint_layer =
+          ToLayoutBoxModelObject(object).Layer();
+    }
     context.current.scroll = context.current.transform->ScrollNode();
     context.current.should_flatten_inherited_transform = false;
   }
@@ -951,12 +973,16 @@ void PaintPropertyTreeBuilder::UpdateOutOfFlowContext(
   if (object.IsLayoutView()) {
     if (RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
       const auto* initial_fixed_transform = context.fixed_position.transform;
+      const auto* initial_fixed_transform_paint_layer =
+          context.fixed_position.transform_paint_layer;
       const auto* initial_fixed_scroll = context.fixed_position.scroll;
 
       context.fixed_position = context.current;
 
       // Fixed position transform and scroll nodes should not be affected.
       context.fixed_position.transform = initial_fixed_transform;
+      context.fixed_position.transform_paint_layer =
+          initial_fixed_transform_paint_layer;
       context.fixed_position.scroll = initial_fixed_scroll;
     }
   } else if (object.CanContainFixedPositionObjects()) {
@@ -1058,6 +1084,20 @@ void PaintPropertyTreeBuilder::UpdatePaintOffset(
           -ToLayoutBox(parent_row)->PhysicalLocation());
     }
   }
+
+  // In the presence of pagination, recompute from scratch the paint offset.
+  // The paint offset for a fragmented LayoutObject is the top-left of its
+  // position in the first fragment in which it participates. See
+  // crbug.com/648274.
+  if (PaintLayer* paint_layer = object.PaintingLayer()) {
+    if (paint_layer->EnclosingPaginationLayer()) {
+      LayoutPoint local_offset = ToLayoutPoint(
+          object.OffsetFromAncestorContainer(&paint_layer->GetLayoutObject()));
+      DCHECK(context.current.transform_paint_layer);
+      context.current.paint_offset = paint_layer->VisualOffsetFromAncestor(
+          context.current.transform_paint_layer, local_offset);
+    }
+  }
 }
 
 void PaintPropertyTreeBuilder::UpdateForObjectLocationAndSize(