Demo patch that demonstrates simple block layout using Layout NG

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

Index: third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc b/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
index 027e1f7589c9a8fa2b1d95ad8880f7980f69f09a..000f2a2e697ca955b65e3df317a89219c9cea29c 100644
--- a/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
+++ b/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
@@ -3,6 +3,11 @@
 // found in the LICENSE file.
 
 #include "core/layout/ng/layout_ng_block_flow.h"
+#include "core/layout/ng/ng_constraint_space.h"
+#include "core/layout/ng/ng_block_layout_algorithm.h"
+#include "core/layout/ng/ng_box_iterator.h"
+#include "core/layout/ng/ng_fragment.h"
+#include "core/layout/LayoutAnalyzer.h"
 
 namespace blink {
 
@@ -13,4 +18,14 @@ bool LayoutNGBlockFlow::isOfType(LayoutObjectType type) const {
   return type == LayoutObjectNGBlockFlow || LayoutBlockFlow::isOfType(type);
 }
 
+void LayoutNGBlockFlow::layoutBlock(bool relayoutChildren) {
+  LayoutAnalyzer::BlockScope analyzer(*this);
+  SubtreeLayoutScope layoutScope(*this);
+
+  const auto& constraintSpace = NGConstraintSpace::fromLayoutObject(*this);
+  NGBox box(this);
+  box.layout(constraintSpace);
+  clearNeedsLayout();
+}
+
 }  // namespace blink