[LayoutNG] Generated break opportunities should not make the line non-empty

Generated break opportunities are not in DOM/box tree, and
that they alone should not make the line non-empty.

Bug: 966817, 969449
Change-Id: Ic718171b45f64f2b66b158e49d98ac0aaffb90a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1634591
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665426}

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

@@ -73,7 +73,7 @@ NGInlineItem::NGInlineItem(NGInlineItemType type,
       end_collapse_type_(kNotCollapsible),
       is_end_collapsible_newline_(false),
       is_symbol_marker_(false),
-      is_generated_(false) {
+      is_generated_for_line_break_(false) {
   DCHECK_GE(end, start);
   ComputeBoxProperties();
 }
@@ -95,7 +95,7 @@ NGInlineItem::NGInlineItem(const NGInlineItem& other,
       end_collapse_type_(other.end_collapse_type_),
       is_end_collapsible_newline_(other.is_end_collapsible_newline_),
       is_symbol_marker_(other.is_symbol_marker_),
-      is_generated_(other.is_generated_) {
+      is_generated_for_line_break_(other.is_generated_for_line_break_) {
   DCHECK_GE(end, start);
 }
 

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

@@ -175,8 +175,8 @@ class CORE_EXPORT NGInlineItem {
   // context that are lost during the whitespace collapsing. This item is used
   // during the line breaking and layout, but is not supposed to generate
   // fragments.
-  bool IsGenerated() const { return is_generated_; }
-  void SetIsGenerated() { is_generated_ = true; }
+  bool IsGeneratedForLineBreak() const { return is_generated_for_line_break_; }
+  void SetIsGeneratedForLineBreak() { is_generated_for_line_break_ = true; }
 
   // Whether the end collapsible space run contains a newline.
   // Valid only when kCollapsible or kCollapsed.
@@ -243,7 +243,7 @@ class CORE_EXPORT NGInlineItem {
   unsigned end_collapse_type_ : 2;  // NGCollapseType
   unsigned is_end_collapsible_newline_ : 1;
   unsigned is_symbol_marker_ : 1;
-  unsigned is_generated_ : 1;
+  unsigned is_generated_for_line_break_ : 1;
   friend class NGInlineNode;
 };
 

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

@@ -271,7 +271,7 @@ void NGInlineItemsBuilderTemplate<OffsetMappingBuilder>::
                                                        nullptr);
   AppendBreakOpportunity(layout_object);
   NGInlineItem* item = &items_->back();
-  item->SetIsGenerated();
+  item->SetIsGeneratedForLineBreak();
   item->SetEndCollapseType(NGInlineItem::kOpaqueToCollapsing);
 }
 

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

@@ -391,7 +391,7 @@ void NGInlineLayoutAlgorithm::PlaceControlItem(const NGInlineItem& item,
     case kZeroWidthSpaceCharacter:
       // Don't generate fragments if this is a generated (not in DOM) break
       // opportunity during the white space collapsing in NGInlineItemBuilder.
-      if (item.IsGenerated())
+      if (item.IsGeneratedForLineBreak())
         return;
       type = NGPhysicalTextFragment::kFlowControl;
       break;

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

@@ -1074,7 +1074,11 @@ void NGLineBreaker::HandleControlItem(const NGInlineItem& item,
     case kZeroWidthSpaceCharacter: {
       // <wbr> tag creates break opportunities regardless of auto_wrap.
       NGInlineItemResult* item_result = AddItem(item, line_info);
-      item_result->should_create_line_box = true;
+      // A generated break opportunity doesn't generate fragments, but we still
+      // need to add this for rewind to find this opportunity. This will be
+      // discarded in |NGInlineLayoutAlgorithm| when it generates fragments.
+      if (!item.IsGeneratedForLineBreak())
+        item_result->should_create_line_box = true;
       item_result->can_break_after = true;
       break;
     }