[FragmentItem] Make NGFragmentItem not a DisplayItemClient

Making |NGFragmentItem| not a |DisplayItemClient| has two
benefits:
1. Give a persistent |DisplayItemClientId| across multiple
   layout cycles.
2. Allow making |Vector<NGFragmentItem>| instead of
   |Vector<scoped_refptr<NGFragmentItem>>|, because a
   |Vector| of |DisplayItemClient| is not allowed.
   This change is expected to reduce the memory allocation
   cost, which is high for text-heavy pages.

This patch is only for 1. The work for 2 will be in following
patches. Still, this patch improves `blink_perf.paint/
paint-offset-changes` microbenchmark by ~10%:
https://pinpoint-dot-chromeperf.appspot.com/job/15b8f60a120000
https://pinpoint-dot-chromeperf.appspot.com/job/14e61bb6120000
and slight positive changes to blink_perf.layout, probably
due to simpler paint invalidations:
https://pinpoint-dot-chromeperf.appspot.com/job/17d3126c120000

This patch is on top of following foudnation patches:
* r770260 <crrev.com/c/2207948> supported |wtf_size_t| for
  fragment id.
* r770637 <crrev.com/c/2209774> added |NGFragment::
  FragmentId()|.

Bug: 982194
Change-Id: I1cb5e2633bd591723632f1acb0cbb09ab4d77f83
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2208586Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771601}

third_party/blink/renderer/core/layout/layout_inline.cc

@@ -1789,12 +1789,22 @@ void LayoutInline::InvalidateDisplayItemClients(
   if (IsInLayoutNGInlineFormattingContext()) {
     if (!ShouldCreateBoxFragment())
       return;
-    NGInlineCursor cursor;
-    for (cursor.MoveTo(*this); cursor; cursor.MoveToNextForSameLayoutObject()) {
-      DCHECK_EQ(cursor.Current().GetLayoutObject(), this);
-      paint_invalidator.InvalidateDisplayItemClient(
-          *cursor.Current().GetDisplayItemClient(), invalidation_reason);
+    if (!RuntimeEnabledFeatures::LayoutNGFragmentItemEnabled()) {
+      NGInlineCursor cursor;
+      for (cursor.MoveTo(*this); cursor;
+           cursor.MoveToNextForSameLayoutObject()) {
+        DCHECK_EQ(cursor.Current().GetLayoutObject(), this);
+        paint_invalidator.InvalidateDisplayItemClient(
+            *cursor.Current().GetDisplayItemClient(), invalidation_reason);
+      }
+      return;
     }
+#if DCHECK_IS_ON()
+    NGInlineCursor cursor;
+    for (cursor.MoveTo(*this); cursor; cursor.MoveToNextForSameLayoutObject())
+      DCHECK_EQ(cursor.Current().GetDisplayItemClient(), this);
+#endif
+    paint_invalidator.InvalidateDisplayItemClient(*this, invalidation_reason);
     return;
   }
 

third_party/blink/renderer/core/layout/layout_text.cc

@@ -2493,11 +2493,21 @@ void LayoutText::InvalidateDisplayItemClients(
   ObjectPaintInvalidator paint_invalidator(*this);
 
   if (IsInLayoutNGInlineFormattingContext()) {
-    NGInlineCursor cursor;
-    for (cursor.MoveTo(*this); cursor; cursor.MoveToNextForSameLayoutObject()) {
-      paint_invalidator.InvalidateDisplayItemClient(
-          *cursor.Current().GetDisplayItemClient(), invalidation_reason);
+    if (!RuntimeEnabledFeatures::LayoutNGFragmentItemEnabled()) {
+      NGInlineCursor cursor;
+      for (cursor.MoveTo(*this); cursor;
+           cursor.MoveToNextForSameLayoutObject()) {
+        paint_invalidator.InvalidateDisplayItemClient(
+            *cursor.Current().GetDisplayItemClient(), invalidation_reason);
+      }
+      return;
     }
+#if DCHECK_IS_ON()
+    NGInlineCursor cursor;
+    for (cursor.MoveTo(*this); cursor; cursor.MoveToNextForSameLayoutObject())
+      DCHECK_EQ(cursor.Current().GetDisplayItemClient(), this);
+#endif
+    paint_invalidator.InvalidateDisplayItemClient(*this, invalidation_reason);
     return;
   }
 

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.cc

@@ -17,8 +17,7 @@ namespace blink {
 
 namespace {
 
-struct SameSizeAsNGFragmentItem : RefCounted<NGFragmentItem>,
-                                  public DisplayItemClient {
+struct SameSizeAsNGFragmentItem : RefCounted<NGFragmentItem> {
   struct {
     void* pointer;
     NGTextOffset text_offset;
@@ -325,7 +324,7 @@ TextDirection NGFragmentItem::ResolvedDirection() const {
   return static_cast<TextDirection>(text_direction_);
 }
 
-String NGFragmentItem::DebugName() const {
+String NGFragmentItem::ToString() const {
   // TODO(yosin): Once |NGPaintFragment| is removed, we should get rid of
   // following if-statements.
   // For ease of rebasing, we use same |DebugName()| as |NGPaintFrgment|.
@@ -357,20 +356,6 @@ String NGFragmentItem::DebugName() const {
   return "NGFragmentItem";
 }
 
-IntRect NGFragmentItem::VisualRect() const {
-  // TODO(kojii): Need to reconsider the storage of |VisualRect|, to integrate
-  // better with |FragmentData| and to avoid dependency to |LayoutObject|.
-  DCHECK(GetLayoutObject());
-  return GetLayoutObject()->VisualRectForInlineBox();
-}
-
-IntRect NGFragmentItem::PartialInvalidationVisualRect() const {
-  // TODO(yosin): Need to reconsider the storage of |VisualRect|, to integrate
-  // better with |FragmentData| and to avoid dependency to |LayoutObject|.
-  DCHECK(GetLayoutObject());
-  return GetLayoutObject()->PartialInvalidationVisualRectForInlineBox();
-}
-
 PhysicalRect NGFragmentItem::LocalVisualRectFor(
     const LayoutObject& layout_object) {
   DCHECK(RuntimeEnabledFeatures::LayoutNGFragmentItemEnabled());

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.h

@@ -29,8 +29,7 @@ struct NGTextFragmentPaintInfo;
 //
 // This class consumes less memory than a full fragment, and can be stored in a
 // flat list (NGFragmentItems) for easier and faster traversal.
-class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
-                                   public DisplayItemClient {
+class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem> {
  public:
   // Represents regular text that exists in the DOM.
   struct TextItem {
@@ -80,7 +79,7 @@ class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
                      const String& text_content,
                      WritingMode writing_mode);
 
-  ~NGFragmentItem() final;
+  ~NGFragmentItem();
 
   ItemType Type() const { return static_cast<ItemType>(type_); }
 
@@ -94,6 +93,7 @@ class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
   bool IsListMarker() const;
 
   // A sequence number of fragments generated from a |LayoutObject|.
+  // For line boxes, please see |kInitialLineFragmentId|.
   wtf_size_t FragmentId() const {
     DCHECK_NE(Type(), kLine);
     return fragment_id_;
@@ -102,6 +102,14 @@ class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
     DCHECK_NE(Type(), kLine);
     fragment_id_ = id;
   }
+  // The initial framgent_id for line boxes.
+  // TODO(kojii): This is to avoid conflict with multicol because line boxes use
+  // its |LayoutBlockFlow| as their |DisplayItemClient|, but multicol also uses
+  // fragment id for |LayoutBlockFlow| today. The plan is to make |FragmentData|
+  // a |DisplayItemClient| instead.
+  // TODO(kojii): The fragment id for line boxes must be unique across NG block
+  // fragmentation. This is not implemented yet.
+  static constexpr wtf_size_t kInitialLineFragmentId = 0x80000000;
 
   // Return true if this is the first fragment generated from a node.
   bool IsFirstForNode() const { return !FragmentId(); }
@@ -137,6 +145,11 @@ class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
   Node* GetNode() const { return layout_object_->GetNode(); }
   Node* NodeForHitTest() const { return layout_object_->NodeForHitTest(); }
 
+  // Use |LayoutObject|+|FragmentId()| for |DisplayItem::Id|.
+  const DisplayItemClient* GetDisplayItemClient() const {
+    return GetLayoutObject();
+  }
+
   wtf_size_t DeltaToNextForSameLayoutObject() const {
     return delta_to_next_for_same_layout_object_;
   }
@@ -205,11 +218,6 @@ class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
     return NGLineBoxType::kNormalLineBox;
   }
 
-  // DisplayItemClient overrides
-  String DebugName() const override;
-  IntRect VisualRect() const override;
-  IntRect PartialInvalidationVisualRect() const override;
-
   static PhysicalRect LocalVisualRectFor(const LayoutObject& layout_object);
 
   // Re-compute the ink overflow for the |cursor| until its end.
@@ -350,6 +358,9 @@ class CORE_EXPORT NGFragmentItem : public RefCounted<NGFragmentItem>,
   // Returns true if this item is reusable.
   bool CanReuse() const;
 
+  // Get a description of |this| for the debug purposes.
+  String ToString() const;
+
  private:
   // Create a text item.
   NGFragmentItem(const NGInlineItem& inline_item,

third_party/blink/renderer/core/layout/ng/inline/ng_inline_cursor.cc

@@ -457,7 +457,7 @@ const DisplayItemClient* NGInlineCursorPosition::GetDisplayItemClient() const {
   if (paint_fragment_)
     return paint_fragment_;
   if (item_)
-    return item_;
+    return item_->GetDisplayItemClient();
   NOTREACHED();
   return nullptr;
 }

third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.cc

@@ -1252,19 +1252,27 @@ inline void NGBoxFragmentPainter::PaintLineBox(
     const DisplayItemClient& display_item_client,
     const NGPaintFragment* line_box_paint_fragment,
     const NGFragmentItem* line_box_item,
+    wtf_size_t line_fragment_id,
     const PaintInfo& paint_info,
     const PhysicalOffset& child_offset) {
   if (paint_info.phase != PaintPhase::kForeground)
     return;
 
+  base::Optional<ScopedDisplayItemFragment> display_item_fragment;
   if (ShouldRecordHitTestData(paint_info)) {
+    if (line_box_item)
+      display_item_fragment.emplace(paint_info.context, line_fragment_id);
     PhysicalRect border_box = line_box_fragment.LocalRect();
     border_box.offset += child_offset;
     paint_info.context.GetPaintController().RecordHitTestData(
         display_item_client, PixelSnappedIntRect(border_box),
         PhysicalFragment().EffectiveAllowedTouchAction());
   }
+
+  // Paint the background of the `::first-line` line box.
   if (NGLineBoxFragmentPainter::NeedsPaint(line_box_fragment)) {
+    if (!display_item_fragment && line_box_item)
+      display_item_fragment.emplace(paint_info.context, line_fragment_id);
     NGLineBoxFragmentPainter line_box_painter(
         line_box_fragment, line_box_paint_fragment, line_box_item,
         PhysicalFragment(), paint_fragment_);
@@ -1343,8 +1351,10 @@ void NGBoxFragmentPainter::PaintLineBoxChildren(
       continue;
     }
     DCHECK(child_fragment.IsLineBox());
-    PaintLineBox(child_fragment, *line, line, /* line_box_item */ nullptr,
-                 paint_info, child_offset);
+    PaintLineBox(
+        child_fragment, *line, line, /* line_box_item */ nullptr,
+        // |line_fragment_id| is used only when |NGFragmentItem| is enabled.
+        /* line_fragment_id */ 0, paint_info, child_offset);
     PaintInlineChildren(line->Children(), paint_info, child_offset);
   }
 }
@@ -1354,6 +1364,7 @@ void NGBoxFragmentPainter::PaintLineBoxChildItems(
     const PaintInfo& paint_info,
     const PhysicalOffset& paint_offset) {
   const bool is_horizontal = box_fragment_.Style().IsHorizontalWritingMode();
+  wtf_size_t line_fragment_id = NGFragmentItem::kInitialLineFragmentId;
   for (; *children; children->MoveToNextSkippingChildren()) {
     const NGFragmentItem* child_item = children->CurrentItem();
     DCHECK(child_item);
@@ -1380,9 +1391,9 @@ void NGBoxFragmentPainter::PaintLineBoxChildItems(
       const NGPhysicalLineBoxFragment* line_box_fragment =
           child_item->LineBoxFragment();
       DCHECK(line_box_fragment);
-      PaintLineBox(*line_box_fragment, *child_item,
+      PaintLineBox(*line_box_fragment, *child_item->GetDisplayItemClient(),
                    /* line_box_paint_fragment */ nullptr, child_item,
-                   paint_info, child_offset);
+                   line_fragment_id++, paint_info, child_offset);
       NGInlineCursor line_box_cursor = children->CursorForDescendants();
       PaintInlineItems(paint_info, paint_offset,
                        child_item->OffsetInContainerBlock(), &line_box_cursor);
@@ -1524,6 +1535,8 @@ void NGBoxFragmentPainter::PaintTextItem(const NGInlineCursor& cursor,
       !(item.IsLineBreak() && HasSelection(item.GetLayoutObject())))
     return;
 
+  ScopedDisplayItemFragment display_item_fragment(paint_info.context,
+                                                  item.FragmentId());
   NGTextFragmentPainter<NGInlineCursor> text_painter(cursor, parent_offset);
   text_painter.Paint(paint_info, paint_offset);
 }

third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.h

@@ -134,6 +134,7 @@ class NGBoxFragmentPainter : public BoxPainterBase {
                     const DisplayItemClient& display_item_client,
                     const NGPaintFragment* line_box_paint_fragment,
                     const NGFragmentItem* line_box_item,
+                    wtf_size_t line_fragment_id,
                     const PaintInfo&,
                     const PhysicalOffset& paint_offset);
   void PaintBackplate(NGInlineCursor* descendants,
@@ -386,7 +387,7 @@ inline NGBoxFragmentPainter::NGBoxFragmentPainter(
     const NGFragmentItem& item,
     const NGPhysicalBoxFragment& fragment)
     : NGBoxFragmentPainter(fragment,
-                           item,
+                           *item.GetDisplayItemClient(),
                            /* paint_fragment */ nullptr,
                            &inline_box_cursor,
                            &item) {

third_party/blink/renderer/core/paint/ng/ng_inline_box_fragment_painter.cc

@@ -17,6 +17,7 @@
 #include "third_party/blink/renderer/core/style/nine_piece_image.h"
 #include "third_party/blink/renderer/platform/graphics/graphics_context_state_saver.h"
 #include "third_party/blink/renderer/platform/graphics/paint/drawing_recorder.h"
+#include "third_party/blink/renderer/platform/graphics/paint/scoped_display_item_fragment.h"
 
 namespace blink {
 
@@ -57,6 +58,12 @@ const NGBorderEdges NGInlineBoxFragmentPainter::BorderEdges() const {
 
 void NGInlineBoxFragmentPainter::Paint(const PaintInfo& paint_info,
                                        const PhysicalOffset& paint_offset) {
+  base::Optional<ScopedDisplayItemFragment> display_item_fragment;
+  if (inline_box_item_) {
+    display_item_fragment.emplace(paint_info.context,
+                                  inline_box_item_->FragmentId());
+  }
+
   const PhysicalOffset adjusted_paint_offset =
       paint_offset + (inline_box_paint_fragment_
                           ? inline_box_paint_fragment_->Offset()
@@ -150,6 +157,14 @@ void NGLineBoxFragmentPainter::PaintBackgroundBorderShadow(
   DCHECK_EQ(paint_info.phase, PaintPhase::kForeground);
   DCHECK_EQ(inline_box_fragment_.Type(), NGPhysicalFragment::kFragmentLineBox);
   DCHECK(NeedsPaint(inline_box_fragment_));
+#if DCHECK_IS_ON()
+  if (RuntimeEnabledFeatures::LayoutNGFragmentItemEnabled()) {
+    DCHECK(inline_box_item_);
+    // |NGFragmentItem| uses the fragment id when painting the background of
+    // line boxes. Please see |NGFragmentItem::kInitialLineFragmentId|.
+    DCHECK_NE(paint_info.context.GetPaintController().CurrentFragment(), 0u);
+  }
+#endif
 
   if (line_style_ == style_ ||
       line_style_.Visibility() != EVisibility::kVisible)

third_party/blink/renderer/core/paint/ng/ng_inline_box_fragment_painter.h

@@ -99,7 +99,7 @@ class NGInlineBoxFragmentPainterBase : public InlineBoxPainterBase {
     if (inline_box_paint_fragment_)
       return *inline_box_paint_fragment_;
     DCHECK(inline_box_item_);
-    return *inline_box_item_;
+    return *inline_box_item_->GetDisplayItemClient();
   }
 
   const virtual NGBorderEdges BorderEdges() const = 0;

third_party/blink/web_tests/flag-specific/layout-ng-fragment-item/paint/invalidation/multi-layout-one-frame-expected.txt

-{
-  "layers": [
-    {
-      "name": "Scrolling Contents Layer",
-      "bounds": [800, 600],
-      "contentsOpaque": true,
-      "backgroundColor": "#FFFFFF",
-      "invalidations": [
-        [193, 8, 189, 22],
-        [12, 11, 53, 16]
-      ]
-    }
-  ]
-}
-