Make LayoutText::SetTextWithOffset() to use slow path for generated break opportunities

This patch changes |NGInlineNodeEditor::Prepare()| to return null for
letting |LayoutText::SetTextWithOffset()| to use slow path when text
content contains generated break opportunity because it is hard to
figure out how many characters removed from text content.

On <b><i><s>ab\n</s>\n</i>\n</b>, text content is "ab\nZZZ",
where "Z" represents U+200B, removing "\n" after "ab" makes text content
to "ab".

Bug: 1125262
Change-Id: I071822dd8be836ee947766ae1877873f35c3af99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2395136
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804671}

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

@@ -238,6 +238,21 @@ TEST_F(LayoutNGTextTest, SetTextWithOffsetDeleteWithBidiControl) {
             GetItemsAsString(*text.GetLayoutObject()));
 }
 
+// http://crbug.com/1125262
+TEST_F(LayoutNGTextTest, SetTextWithOffsetDeleteWithGeneratedBreakOpportunity) {
+  if (!RuntimeEnabledFeatures::LayoutNGEnabled())
+    return;
+
+  InsertStyleElement("#target { white-space:nowrap; }");
+  SetBodyInnerHTML(u"<p><b><i id=target>ab\n</i>\n</b>\n</div>");
+  // We have two ZWS for "</i>\n" and "</b>\n".
+  Text& text = To<Text>(*GetElementById("target")->firstChild());
+  text.deleteData(2, 1, ASSERT_NO_EXCEPTION);  // remove "\n"
+
+  EXPECT_EQ("LayoutText has NeedsCollectInlines",
+            GetItemsAsString(*text.GetLayoutObject()));
+}
+
 // http://crbug.com/1123251
 TEST_F(LayoutNGTextTest, SetTextWithOffsetEditingTextCollapsedSpace) {
   if (!RuntimeEnabledFeatures::LayoutNGEnabled())

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

@@ -277,6 +277,7 @@ void NGInlineItemsBuilderTemplate<OffsetMappingBuilder>::
   typename OffsetMappingBuilder::SourceNodeScope scope(&mapping_builder_,
                                                        nullptr);
   NGInlineItem& item = AppendBreakOpportunity(layout_object);
+  has_generated_break_opportunity_ = true;
   item.SetIsGeneratedForLineBreak();
   item.SetEndCollapseType(NGInlineItem::kOpaqueToCollapsing);
 }
@@ -1239,6 +1240,7 @@ void NGInlineItemsBuilderTemplate<
   // |SegmentText()| will analyze the text and reset |is_bidi_enabled_| if it
   // doesn't contain any RTL characters.
   data->is_bidi_enabled_ = MayBeBidiEnabled();
+  data->has_generated_break_opportunity_ = HasGeneratedBreakOpportunity();
   // Note: Even if |IsEmptyInline()| is true, |text_| isn't empty, e.g. it
   // holds U+FFFC(ORC) for float or abspos.
   data->has_line_even_if_empty_ =

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

@@ -56,6 +56,11 @@ class NGInlineItemsBuilderTemplate {
   // Returns whether the items contain any Bidi controls.
   bool HasBidiControls() const { return has_bidi_controls_; }
 
+  // Returns whether the items contain any generated break opportunity.
+  bool HasGeneratedBreakOpportunity() const {
+    return has_generated_break_opportunity_;
+  }
+
   // Returns if the inline node has no content. For example:
   // <span></span> or <span><float></float></span>.
   bool IsEmptyInline() const { return is_empty_inline_; }
@@ -182,6 +187,7 @@ class NGInlineItemsBuilderTemplate {
 
   bool has_bidi_controls_ = false;
   bool has_ruby_ = false;
+  bool has_generated_break_opportunity_ = false;
   bool is_empty_inline_ = true;
   bool is_block_level_ = true;
   bool changes_may_affect_earlier_lines_ = false;

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

@@ -522,7 +522,8 @@ class NGInlineNodeDataEditor final {
         block_flow_->NeedsLayout() ||
         block_flow_->GetDocument().NeedsLayoutTreeUpdate() ||
         !block_flow_->GetNGInlineNodeData() ||
-        block_flow_->GetNGInlineNodeData()->text_content.IsNull())
+        block_flow_->GetNGInlineNodeData()->text_content.IsNull() ||
+        block_flow_->GetNGInlineNodeData()->HasGeneratedBreakOpportunity())
       return nullptr;
 
     // Because of current text content has secured text, e.g. whole text is

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

@@ -22,6 +22,10 @@ struct CORE_EXPORT NGInlineNodeData : NGInlineItemsData {
     return static_cast<TextDirection>(base_direction_);
   }
 
+  bool HasGeneratedBreakOpportunity() const {
+    return has_generated_break_opportunity_;
+  }
+
   bool HasLineEvenIfEmpty() const { return has_line_even_if_empty_; }
   bool HasRuby() const { return has_ruby_; }
   bool IsEmptyInline() const { return is_empty_inline_; }
@@ -58,6 +62,10 @@ struct CORE_EXPORT NGInlineNodeData : NGInlineItemsData {
   unsigned is_bidi_enabled_ : 1;
   unsigned base_direction_ : 1;  // TextDirection
 
+  // True if text content has U+200B, zero width space, representing generated
+  // break opportunity.
+  unsigned has_generated_break_opportunity_ : 1;
+
   // True if there are no inline item items and the associated block is root
   // editable element or having "-internal-empty-line-height:fabricated",
   // e.g. <div contenteditable></div>, <input type=button value="">