[LayoutNG] Add box fragments to line boxes when needed

third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc

Index: third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
index b8739da255de2b2cd3743f47ebb26e120611dd16..baed4d6e70b4aed0a855943f61c291982db1628c 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
@@ -22,8 +22,16 @@ NGFragmentBuilder::NGFragmentBuilder(NGPhysicalFragment::NGFragmentType type,
       writing_mode_(kHorizontalTopBottom),
       direction_(TextDirection::kLtr),
       node_(node),
-      did_break_(false) {
-}
+      layout_object_(node->GetLayoutObject()),
+      did_break_(false) {}
+
+NGFragmentBuilder::NGFragmentBuilder(NGPhysicalFragment::NGFragmentType type,
+                                     LayoutObject* layout_object)
+    : type_(type),
+      writing_mode_(kHorizontalTopBottom),
+      direction_(TextDirection::kLtr),
+      layout_object_(layout_object),
+      did_break_(false) {}
 
 NGFragmentBuilder& NGFragmentBuilder::SetWritingMode(
     NGWritingMode writing_mode) {
@@ -85,8 +93,10 @@ NGFragmentBuilder& NGFragmentBuilder::AddChild(
   switch (child->Type()) {
     case NGPhysicalBoxFragment::kFragmentBox:
       // Update if we have fragmented in this flow.
-      did_break_ |= !child->BreakToken()->IsFinished();
-      child_break_tokens_.push_back(child->BreakToken());
+      if (child->BreakToken()) {
+        did_break_ |= !child->BreakToken()->IsFinished();
+        child_break_tokens_.push_back(child->BreakToken());
+      }
       break;
     case NGPhysicalBoxFragment::kFragmentLineBox:
       // NGInlineNode produces multiple line boxes in an anonymous box. Only
@@ -193,16 +203,18 @@ RefPtr<NGLayoutResult> NGFragmentBuilder::ToBoxFragment() {
   }
 
   RefPtr<NGBreakToken> break_token;
-  if (last_inline_break_token_) {
-    DCHECK(!last_inline_break_token_->IsFinished());
-    child_break_tokens_.push_back(std::move(last_inline_break_token_));
-    did_break_ = true;
-  }
-  if (did_break_) {
-    break_token = NGBlockBreakToken::Create(node_.Get(), used_block_size_,
-                                            child_break_tokens_);
-  } else {
-    break_token = NGBlockBreakToken::Create(node_.Get());
+  if (node_) {
+    if (last_inline_break_token_) {
+      DCHECK(!last_inline_break_token_->IsFinished());
+      child_break_tokens_.push_back(std::move(last_inline_break_token_));
+      did_break_ = true;
+    }
+    if (did_break_) {
+      break_token = NGBlockBreakToken::Create(node_.Get(), used_block_size_,
+                                              child_break_tokens_);
+    } else {
+      break_token = NGBlockBreakToken::Create(node_.Get());
+    }
   }
 
   for (auto& positioned_float : positioned_floats_) {
@@ -214,9 +226,9 @@ RefPtr<NGLayoutResult> NGFragmentBuilder::ToBoxFragment() {
   }
 
   RefPtr<NGPhysicalBoxFragment> fragment = AdoptRef(new NGPhysicalBoxFragment(
-      node_->GetLayoutObject(), physical_size,
-      overflow_.ConvertToPhysical(writing_mode_), children_, positioned_floats_,
-      bfc_offset_, end_margin_strut_, std::move(break_token)));
+      layout_object_, physical_size, overflow_.ConvertToPhysical(writing_mode_),
+      children_, positioned_floats_, bfc_offset_, end_margin_strut_,
+      std::move(break_token)));
 
   return AdoptRef(
       new NGLayoutResult(std::move(fragment), out_of_flow_descendants_,