[layoutng] async layout part 1: Change the API to support async

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.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 "core/CoreExport.h"
 #include "core/layout/ng/ng_box.h"
 #include "core/layout/ng/ng_box_iterator.h"
@@ skipping 13 matching lines @@
   // Default constructor.
   // @param style Style reference of the block that is being laid out.
   // @param boxIterator Iterator for the block's children.
   NGBlockLayoutAlgorithm(PassRefPtr<const ComputedStyle>, NGBoxIterator);
 
   // 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*) override;
+  // Returns true when done; when this function returns false, it has to be
+  // called again. The out parameter will only be set when this function
+  // returns true. The same constraint space has to be passed each time.
+  bool Layout(const NGConstraintSpace*, NGFragment**) override;
 
  private:
-  RefPtr<const ComputedStyle> m_style;
-  NGBoxIterator m_boxIterator;
+  RefPtr<const ComputedStyle> style_;
+  NGBoxIterator box_iterator_;
 };
 
 }  // namespace blink
 
 #endif  // NGBlockLayoutAlgorithm_h