[LayoutNG] Allow block-flow layout to be fragmented using new approach.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/ng/ng_fragment_builder.h"
 
+#include "core/layout/ng/ng_block_break_token.h"
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_fragment.h"
 #include "core/layout/ng/ng_physical_box_fragment.h"
 #include "core/layout/ng/ng_physical_text_fragment.h"
+#include "platform/heap/Handle.h"
 
 namespace blink {
 
 // TODO(ikilpatrick): Make writing mode and direction be in the constructor.
 NGFragmentBuilder::NGFragmentBuilder(NGPhysicalFragment::NGFragmentType type,
                                      NGLayoutInputNode* node)
     : type_(type),
       writing_mode_(kHorizontalTopBottom),
       direction_(TextDirection::kLtr),
-      node_(node) {}
+      node_(node),
+      did_break_(false) {
+  child_break_tokens_ = new HeapVector<Member<NGBreakToken>>();
+}
 
 NGFragmentBuilder& NGFragmentBuilder::SetWritingMode(
     NGWritingMode writing_mode) {
   writing_mode_ = writing_mode;
   return *this;
 }
 
 NGFragmentBuilder& NGFragmentBuilder::SetDirection(TextDirection direction) {
   direction_ = direction;
   return *this;
@@ skipping 37 matching lines @@
 
   return AddChild(child->PhysicalFragment(), child_offset);
 }
 
 NGFragmentBuilder& NGFragmentBuilder::AddChild(
     RefPtr<NGPhysicalFragment> child,
     const NGLogicalOffset& child_offset) {
   DCHECK_EQ(type_, NGPhysicalFragment::kFragmentBox)
       << "Only box fragments can have children";
 
+  if (child->Type() == NGPhysicalBoxFragment::NGFragmentType::kFragmentBox &&

[Gleb Lanbin, 2017/02/24 21:51:28]

just
did_break_ = child->Type() == 
NGPhysicalBoxFragment::NGFragmentType::kFragmentBox &&
!child->BreakToken()->IsFinished();

or better add IsBox/IsText method to NGPhysicalBoxFragment so you can write
something like
did_break_ = child->IsBox() && !child->BreakToken()->IsFinished();

[ikilpatrick, 2017/02/25 00:57:22]

Done.

+      !child->BreakToken()->IsFinished()) {
+    // We have an unfinished child, we must produce an unfinished break token.
+    did_break_ = true;
+  }
+
+  child_break_tokens_->push_back(child->BreakToken());
   children_.push_back(std::move(child));
   offsets_.push_back(child_offset);
 
   return *this;
 }
 
 NGFragmentBuilder& NGFragmentBuilder::AddFloatingObject(
     NGFloatingObject* floating_object,
     const NGLogicalOffset& floating_object_offset) {
   positioned_floats_.push_back(floating_object);
@@ skipping 61 matching lines @@
   out_of_flow_descendants_.add(descendant);
   out_of_flow_positions_.push_back(position);
   return *this;
 }
 
 RefPtr<NGLayoutResult> NGFragmentBuilder::ToBoxFragment() {
   // TODO(layout-ng): Support text fragments
   DCHECK_EQ(type_, NGPhysicalFragment::kFragmentBox);
   DCHECK_EQ(offsets_.size(), children_.size());
 
-  auto* break_token = break_token_.get();
-  break_token_ = nullptr;
-
   NGPhysicalSize physical_size = size_.ConvertToPhysical(writing_mode_);
 
   for (size_t i = 0; i < children_.size(); ++i) {
     NGPhysicalFragment* child = children_[i].get();
     child->SetOffset(offsets_[i].ConvertToPhysical(
         writing_mode_, direction_, physical_size, child->Size()));
   }
 
   Vector<Persistent<NGFloatingObject>> positioned_floats;
   positioned_floats.reserveCapacity(positioned_floats_.size());
 
+  Persistent<NGBreakToken> break_token;
+  if (did_break_) {
+    break_token =
+        new NGBlockBreakToken(toNGBlockNode(node_.get()), used_block_size_,
+                              *child_break_tokens_.get());
+  } else {
+    break_token = new NGBlockBreakToken(node_.get());
+  }
+
   for (size_t i = 0; i < positioned_floats_.size(); ++i) {
     Persistent<NGFloatingObject>& floating_object = positioned_floats_[i];
     NGPhysicalFragment* floating_fragment = floating_object->fragment.get();
     floating_fragment->SetOffset(floating_object_offsets_[i].ConvertToPhysical(
         writing_mode_, direction_, physical_size, floating_fragment->Size()));
     positioned_floats.push_back(floating_object);
   }
 
   RefPtr<NGPhysicalBoxFragment> fragment = adoptRef(new NGPhysicalBoxFragment(
       node_->GetLayoutObject(), physical_size,
@@ skipping 16 matching lines @@
   Vector<Persistent<NGFloatingObject>> empty_unpositioned_floats;
   Vector<Persistent<NGFloatingObject>> empty_positioned_floats;
 
   return adoptRef(new NGPhysicalTextFragment(
       node_->GetLayoutObject(), toNGInlineNode(node_), index, start_offset,
       end_offset, size_.ConvertToPhysical(writing_mode_),
       overflow_.ConvertToPhysical(writing_mode_)));
 }
 
 }  // namespace blink