[LayoutNG] Very simple layout() implementation

third_party/WebKit/Source/core/layout/ng/NGBlockLayoutAlgorithm.h

 // 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.
 
 #ifndef NGBlockLayoutAlgorithm_h
 #define NGBlockLayoutAlgorithm_h
 
+#include "wtf/RefPtr.h"
+
 namespace blink {
 
+class ComputedStyle;
+class LayoutBox;
+class NGConstraintSpace;
+class NGFragment;
+
+// A class for general block layout (e.g. a <div> with no special style).
+// Lays out the children in sequence.
 class NGBlockLayoutAlgorithm {
 public:
-    NGBlockLayoutAlgorithm();
+    NGBlockLayoutAlgorithm(const ComputedStyle*);
+
+    // Actual layout implementation. Lays out the children in sequence within
+    // the constraints given by the NGConstraintSpace. Returns a fragment
+    // with the resulting layout information.
+    // This function can not be const because for interruptible layout, we have
+    // to be able to store state information.
+    NGFragment* layout(const NGConstraintSpace&);
+private:
+    RefPtr<const ComputedStyle> m_style;
 };
 
 } // namespace blink
 
 #endif // NGBlockLayoutAlgorithm_h