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

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.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_block_layout_algorithm.h"
 
 #include "core/layout/LayoutBox.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_fragment_builder.h"
 #include "core/layout/ng/ng_fragment.h"
 #include "core/layout/ng/ng_length_utils.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/LengthFunctions.h"
 
 namespace blink {
 
 NGBlockLayoutAlgorithm::NGBlockLayoutAlgorithm(
     PassRefPtr<const ComputedStyle> style,
     NGBoxIterator box_iterator)
-    : m_style(style), m_boxIterator(box_iterator) {}
+    : style_(style), box_iterator_(box_iterator) {}
 
-NGFragment* NGBlockLayoutAlgorithm::layout(
-    const NGConstraintSpace* constraint_space) {
+bool NGBlockLayoutAlgorithm::Layout(const NGConstraintSpace* constraint_space,
+                                    NGFragment** out) {
   LayoutUnit inline_size =
-      computeInlineSizeForFragment(*constraint_space, *m_style);
+      computeInlineSizeForFragment(*constraint_space, *style_);
   // TODO(layout-ng): For quirks mode, should we pass blockSize instead of -1?
   LayoutUnit block_size =
-      computeBlockSizeForFragment(*constraint_space, *m_style, LayoutUnit(-1));
+      computeBlockSizeForFragment(*constraint_space, *style_, LayoutUnit(-1));
   NGConstraintSpace* constraint_space_for_children = new NGConstraintSpace(
       *constraint_space, NGLogicalSize(inline_size, block_size));
 
   NGFragmentBuilder builder(NGFragmentBase::FragmentBox);
   builder.SetInlineSize(inline_size).SetBlockSize(block_size);
 
   LayoutUnit content_size;
-  for (NGBox box : m_boxIterator) {
+  for (NGBox box : box_iterator_) {
     NGBoxStrut child_margins =
         computeMargins(*constraint_space_for_children, *box.style());
-    NGFragment* fragment = box.layout(constraint_space_for_children);
+    NGFragment* fragment;
+    // TODO(layout-ng): Actually make this async
+    while (!box.Layout(constraint_space_for_children, &fragment))
+      ;
     // TODO(layout-ng): Support auto margins
     fragment->SetOffset(child_margins.inline_start,
                         content_size + child_margins.block_start);
     box.positionUpdated(*fragment);
     content_size += fragment->BlockSize() + child_margins.BlockSum();
     builder.AddChild(fragment);
   }
 
   // Recompute the block-axis size now that we know our content size.
   block_size =
-      computeBlockSizeForFragment(*constraint_space, *m_style, content_size);
+      computeBlockSizeForFragment(*constraint_space, *style_, content_size);
 
   // TODO(layout-ng): Compute correct inline overflow (block overflow should be
   // correct)
   builder.SetBlockSize(block_size)
       .SetInlineOverflow(inline_size)
       .SetBlockOverflow(content_size);
-  return builder.ToFragment();
+  *out = builder.ToFragment();
+  return true;
 }
 
 }  // namespace blink