Revert "Let SelectionPaintRange iterator iterate on a flat tree."

This reverts commit deb6bb60.

Reason for revert: This causes much crash on clusterfuzz.
Original change's description:
> Let SelectionPaintRange iterator iterate on a flat tree.
> 
> SelectionPaintRange::Iterator iterated LayoutObjects using layout order
> but we marks SelectionStatus on flat tree order.
> This causes invalidation leak if they are not same order.
> Ruby element is a reported example for that.
> 
> This patch changes SelectionPaintRange::Iterator iterate on a flat tree
> considering first-letter.
> 
> Bug: 843144
> Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
> Change-Id: I02cbad86e64d0a7781f8fb37e2d13c7aa00228fb
> Reviewed-on: https://chromium-review.googlesource.com/1063521
> Commit-Queue: Yoichi Osato <yoichio@chromium.org>
> Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
> Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#569168}

TBR=yosin@chromium.org,yoichio@chromium.org,xiaochengh@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 843144, 855026
Change-Id: I745ab57ed70bd10e59bac20cf4f6fd591e170abd
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Reviewed-on: https://chromium-review.googlesource.com/1118098Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Yoichi Osato <yoichio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571076}

third_party/blink/renderer/core/editing/layout_selection.cc

@@ -76,49 +76,13 @@ base::Optional<unsigned> SelectionPaintRange::EndOffset() const {
   return end_offset_;
 }
 
-static LayoutTextFragment* FirstLetterPartFor(
-    const LayoutObject* layout_object) {
-  if (!layout_object->IsText())
-    return nullptr;
-  if (!ToLayoutText(layout_object)->IsTextFragment())
-    return nullptr;
-  return ToLayoutTextFragment(const_cast<LayoutObject*>(
-      AssociatedLayoutObjectOf(*layout_object->GetNode(), 0)));
-}
-
-static LayoutObject* NextLayoutObjectOnFlatTree(
-    const LayoutObject& layout_object) {
-  // If |layout_object| is a first letter part, return remaining part.
-  if (layout_object.IsText() && ToLayoutText(layout_object).IsTextFragment() &&
-      !ToLayoutTextFragment(layout_object).IsRemainingTextLayoutObject()) {
-    const Node* associated_node =
-        ToLayoutTextFragment(layout_object).AssociatedTextNode();
-    if (!associated_node)
-      return nullptr;
-    return associated_node->GetLayoutObject();
-  }
-  // Otherwise, find the first layouted object of following nodes.
-  const Node* node = layout_object.GetNode();
-  DCHECK(node);
-  for (const Node* next = FlatTreeTraversal::Next(*node); next;
-       next = FlatTreeTraversal::Next(*next)) {
-    LayoutObject* layout_object = next->GetLayoutObject();
-    if (!layout_object)
-      continue;
-    if (LayoutObject* first_letter = FirstLetterPartFor(layout_object))
-      return first_letter;
-    return layout_object;
-  }
-  return nullptr;
-}
-
 SelectionPaintRange::Iterator::Iterator(const SelectionPaintRange* range) {
   if (!range || range->IsNull()) {
     current_ = nullptr;
     return;
   }
   current_ = range->StartLayoutObject();
-  stop_ = NextLayoutObjectOnFlatTree(*range->EndLayoutObject());
+  stop_ = range->EndLayoutObject()->NextInPreOrder();
 }
 
 LayoutObject* SelectionPaintRange::Iterator::operator*() const {
@@ -128,7 +92,7 @@ LayoutObject* SelectionPaintRange::Iterator::operator*() const {
 
 SelectionPaintRange::Iterator& SelectionPaintRange::Iterator::operator++() {
   DCHECK(current_);
-  current_ = NextLayoutObjectOnFlatTree(*current_);
+  current_ = current_->NextInPreOrder();
   if (current_ && current_ != stop_)
     return *this;
 
@@ -461,6 +425,15 @@ static base::Optional<unsigned> ComputeEndOffset(
   return ToText(layout_node)->length();
 }
 
+static LayoutTextFragment* FirstLetterPartFor(LayoutObject* layout_object) {
+  if (!layout_object->IsText())
+    return nullptr;
+  if (!ToLayoutText(layout_object)->IsTextFragment())
+    return nullptr;
+  return ToLayoutTextFragment(const_cast<LayoutObject*>(
+      AssociatedLayoutObjectOf(*layout_object->GetNode(), 0)));
+}
+
 static void MarkSelected(SelectedLayoutObjects* selected_objects,
                          LayoutObject* layout_object,
                          SelectionState state) {

third_party/blink/renderer/core/editing/layout_selection_test.cc

@@ -76,20 +76,18 @@ using IsTypeOfSimple = bool(const LayoutObject& layout_object);
     return layout_object.member_func();                        \
   }
 
-USING_LAYOUTOBJECT_FUNC(IsBR);
 USING_LAYOUTOBJECT_FUNC(IsLayoutBlock);
 USING_LAYOUTOBJECT_FUNC(IsLayoutBlockFlow);
-USING_LAYOUTOBJECT_FUNC(IsLayoutButton);
-USING_LAYOUTOBJECT_FUNC(IsLayoutEmbeddedContent);
-USING_LAYOUTOBJECT_FUNC(IsLayoutImage);
-USING_LAYOUTOBJECT_FUNC(IsLayoutInline);
 USING_LAYOUTOBJECT_FUNC(IsLayoutNGBlockFlow);
+USING_LAYOUTOBJECT_FUNC(IsLayoutInline);
+USING_LAYOUTOBJECT_FUNC(IsBR);
 USING_LAYOUTOBJECT_FUNC(IsListItem);
 USING_LAYOUTOBJECT_FUNC(IsListMarker);
-USING_LAYOUTOBJECT_FUNC(IsRuby);
-USING_LAYOUTOBJECT_FUNC(IsRubyText);
+USING_LAYOUTOBJECT_FUNC(IsLayoutImage);
+USING_LAYOUTOBJECT_FUNC(IsLayoutButton);
 USING_LAYOUTOBJECT_FUNC(IsSVGRoot);
 USING_LAYOUTOBJECT_FUNC(IsSVGText);
+USING_LAYOUTOBJECT_FUNC(IsLayoutEmbeddedContent);
 
 static IsTypeOf IsLayoutTextFragmentOf(const String& text) {
   return WTF::BindRepeating(
@@ -688,41 +686,6 @@ TEST_F(LayoutSelectionTest, Embed) {
   TEST_NO_NEXT_LAYOUT_OBJECT();
 }
 
-// http:/crbug.com/843144
-TEST_F(LayoutSelectionTest, Ruby) {
-  Selection().SetSelectionAndEndTyping(
-      SetSelectionTextToBody("^<ruby>foo<rt>bar</rt></ruby>|"));
-  Selection().CommitAppearanceIfNeeded();
-  TEST_NEXT(IsLayoutBlock, kContain, NotInvalidate);
-  TEST_NEXT(IsRuby, kNone, NotInvalidate);
-  TEST_NEXT(IsLayoutBlock, kContain, NotInvalidate);
-  TEST_NEXT(IsRubyText, kContain, NotInvalidate);
-  TEST_NEXT("bar", kEnd, ShouldInvalidate);
-  TEST_NEXT(IsLayoutBlock, kContain, NotInvalidate);
-  TEST_NEXT("foo", kStart, ShouldInvalidate);
-  TEST_NO_NEXT_LAYOUT_OBJECT();
-
-  UpdateAllLifecyclePhases();
-  TEST_NEXT(IsLayoutBlock, kContain, NotInvalidate);
-  TEST_NEXT(IsRuby, kNone, NotInvalidate);
-  TEST_NEXT(IsLayoutBlock, kContain, NotInvalidate);
-  TEST_NEXT(IsRubyText, kContain, NotInvalidate);
-  TEST_NEXT("bar", kEnd, NotInvalidate);
-  TEST_NEXT(IsLayoutBlock, kContain, NotInvalidate);
-  TEST_NEXT("foo", kStart, NotInvalidate);
-  TEST_NO_NEXT_LAYOUT_OBJECT();
-
-  Selection().ClearLayoutSelection();
-  TEST_NEXT(IsLayoutBlock, kNone, NotInvalidate);
-  TEST_NEXT(IsRuby, kNone, NotInvalidate);
-  TEST_NEXT(IsLayoutBlock, kNone, NotInvalidate);
-  TEST_NEXT(IsRubyText, kNone, NotInvalidate);
-  TEST_NEXT("bar", kNone, ShouldInvalidate);
-  TEST_NEXT(IsLayoutBlock, kNone, NotInvalidate);
-  TEST_NEXT("foo", kNone, ShouldInvalidate);
-  TEST_NO_NEXT_LAYOUT_OBJECT();
-}
-
 static const NGPaintFragment* FindNGPaintFragmentInternal(
     const NGPaintFragment* paint,
     const LayoutObject* layout_object) {