[LayoutNG] WIP on storing layout output in the legacy tree for multicol.

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

Index: third_party/WebKit/Source/core/layout/ng/ng_block_node.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_block_node.cc b/third_party/WebKit/Source/core/layout/ng/ng_block_node.cc
index a22cbda1f39230492c9c7a24ee14995ec2a683d0..cb26550411c84fc23a70b9d15de1d96191712d2d 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_block_node.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_block_node.cc
@@ -5,6 +5,8 @@
 #include "core/layout/ng/ng_block_node.h"
 
 #include "core/layout/LayoutBlockFlow.h"
+#include "core/layout/LayoutMultiColumnFlowThread.h"
+#include "core/layout/LayoutMultiColumnSet.h"
 #include "core/layout/api/LineLayoutAPIShim.h"
 #include "core/layout/line/InlineIterator.h"
 #include "core/layout/ng/layout_ng_block_flow.h"
@@ -238,6 +240,29 @@ void NGBlockNode::CopyFragmentDataToLayoutBox(
   NGPhysicalBoxFragment* fragment =
       toNGPhysicalBoxFragment(layout_result->PhysicalFragment().get());
 
+  if (layout_box_->style()->specifiesColumns()) {
+    LayoutBlockFlow* multicol = toLayoutBlockFlow(layout_box_);

[Gleb Lanbin, 2017/03/31 22:33:29]

can you move this logic into a separate function declared in the unnamed
namespace, e.g. UpdateLegacyMultiFlowThread?

if (layout_box_->style()->specifiesColumns())
  UpdateLegacyMultiFlowThread(layout_box_, fragment);

[mstensho (USE GERRIT), 2017/04/03 10:20:11]

Done.

+    if (auto* flow_thread = multicol->multiColumnFlowThread()) {
+      if (auto* column_set = flow_thread->firstMultiColumnSet()) {
+        column_set->setWidth(fragment->Width());
+        column_set->setHeight(fragment->Height());
+
+        // TODO(mstensho): This value has next to nothing to do with the flow
+        // thread portion size, but at least it's usually better than zero.
+        column_set->endFlow(fragment->Height());
+
+        column_set->clearNeedsLayout();
+      }
+      // TODO(mstensho): Fix the relatively nonsensical values here (the
+      // content box size of the multicol container has very little to do with
+      // the price of eggs).
+      flow_thread->setWidth(fragment->Width());
+      flow_thread->setHeight(fragment->Height());
+
+      flow_thread->validateColumnSets();
+      flow_thread->clearNeedsLayout();
+    }
+  }
   layout_box_->setWidth(fragment->Width());
   layout_box_->setHeight(fragment->Height());
   NGBoxStrut border_and_padding = ComputeBorders(constraint_space, Style()) +