[LayoutNG] Make line dirty marking faster

This patch changes |NGPaintFragment::MarkLineBoxesDirtyFor()| and
|NGPaintFragment::TryMarkLineBoxDirtyFor()| to mark only first line of layout
object and stop scanning descendnats of culld inline box.

Speed improvement for layout/attach-inlines.html is
26.50 runs/s[1] to 68.45 run/s

Note: without marking dirty line, speed is 73.50 runs/s

[1] http://crrev.com/c/1248622 [LayoutNG] Make line dirty marking faster

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I897224f3bd7a19036718da79bf97d0fa0076cd3d
Reviewed-on: https://chromium-review.googlesource.com/1251263
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595390}

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

@@ -538,18 +538,6 @@ void NGPaintFragment::MarkLineBoxesDirtyFor(const LayoutObject& layout_object) {
   DCHECK(layout_object.IsInline()) << layout_object;
   if (TryMarkLineBoxDirtyFor(layout_object))
     return;
-  if (layout_object.IsLayoutInline()) {
-    bool marked = false;
-    for (LayoutObject* runner = layout_object.NextInPreOrder(&layout_object);
-         runner; runner = runner->NextInPreOrder(&layout_object)) {
-      if (runner->IsFloatingOrOutOfFlowPositioned())
-        continue;
-      if (TryMarkLineBoxDirtyFor(*runner))
-        marked = true;
-    }
-    if (marked)
-      return;
-  }
   // Since |layout_object| isn't in fragment tree, check preceding siblings.
   // Note: Once we reuse lines below dirty lines, we should check next siblings.
   for (LayoutObject* previous = layout_object.PreviousSibling(); previous;
@@ -589,19 +577,14 @@ void NGPaintFragment::MarkLineBoxDirty() {
 
 bool NGPaintFragment::TryMarkLineBoxDirtyFor(
     const LayoutObject& layout_object) {
-  if (!layout_object.IsInLayoutNGInlineFormattingContext())
-    return false;
-  const auto& range = InlineFragmentsFor(&layout_object);
-  if (range.IsEmpty())
-    return false;
-  NGPaintFragment* last_parent = nullptr;
-  for (NGPaintFragment* fragment : range) {
-    if (last_parent == fragment->Parent())
-      continue;
-    fragment->MarkLineBoxDirty();
-    last_parent = fragment->Parent();
-  }
+  // Once we reuse lines below dirty lines, we should mark lines for all
+  // inline fragments.
+  NGPaintFragment* const first_fragment = layout_object.FirstInlineFragment();
+  if (first_fragment) {
+    first_fragment->MarkLineBoxDirty();
     return true;
+  }
+  return false;
 }
 
 void NGPaintFragment::SetShouldDoFullPaintInvalidationRecursively() {